really frustrated

I was riding this horse at the old barn I rode at. He was good for me, lazy but good. If I had a crop in my hand I didn't have to use it, but if I didn't he would require constant leg. Oh, he's a 7 year old TBx. Anyway, so his owner moved him to this new barn and I agreed to lease him because she needed help with the board and I want to have a horse to ride. The terms of the lease are really good and the price can't be beat, we are kinda friends so I guess that's why. In any case, at the new barn he is being a total jerk to me. The first time I rode him at the new barn was at a lesson. He was a total pain. I was 'fighting' with him the whole time. He was constantly trying to snatch the reigns out of my hands, he kept stopping and refusing to move forward, when I pressed him to move forward he would start backing up and I had to redirect him to get him moving forward again. I about put my right hip out of whack trying to get him to pick up the left lead canter because he just wouldn't. I think he made me pull a muscle in my back with the constant reign snatching because by the end of the lesson I couldn't physically sit up straight because it hurt that muscle too much. The next time I rode him he was better but still did the reign snatching thing from time to time, mostly at the walk. I was asked to not canter him because his owner said he seemed sore after my lesson - oh I should mention he wasn't ridden much at the old barn, maybe once a week or so. So I've ridden him three times. Once at the lesson, again a couple days later and the third time yesterday. He seemed better yesterday until I tried to ride him back to the barn from the riding field. I don't know what his deal was but he started with the stopping and backing thing again, nearly backed himself up into a pond! I think maybe because I specifically took a different 'line' riding back to the barn so he wouldn't associate one direction with going back. His owner rode him after the first time I rode him and said he was good, only tugged on the reigns a little and picked up the left lead canter right away for her.
Now I know there's a difference between us, she is a more experienced rider and he is HER horse so they have a bond. I'm frustrated because I was really looking forward to riding him at this new barn because the riding area is so much nicer and there's more room but he's being such a jerk about me riding him I can't really enjoy it. But I keep telling myself I need to be 'challenged' by a horse to become a better rider, right? It's just a little un-nerving to me when he pins his ears back and starts backing up when I want him to go forward. He has never really bucked but he does kick out with one hind leg or 'crow hops' occassionally. And I know horses can sense a 'nervous' rider so I'm always quick to take a deep breath and relax as soon as I start feeling nervous.
I'M SO FRUSTRATED THOUGH!!! Should I be riding this horse and keep myself challenged or look for another horse that would be more 'suited' to me? I am taking weekly lessons so that I know I am asking and correcting the way that I should and it makes me feel a little more confident when the trainer tells me what to do and why he's doing what. Everyone keeps saying that he's 'testing' me. When does the testing period end?!

Hate to break it to you, but the "testing period" never really ends. Some horses, especially dominant horses, will ALWAYS be testing your dominance. Just focus on some ground work to tell him you are the boss.
Quick question for you- how long was he at the new barn before you rode him? Is he good with being transported? He could just be stressed because of the move especially if he was at the old place for awhile.

It was the third day after he was moved that I rode him. He was moved on a sunday night, the owner rode him on tuesday and he was 'a handful' wanted to run around, calling to his new pasture buddies etc... I rode him wednesday. The trainer and everyone kept saying he was acting up because it was 'new', the place and all and people keep telling me he'll get better as he gets used to the new place. He is generally good for being transported (as I am told) but he recently had a bad experience in the wash rack at the old barn and has since become 'claustraphobic' in certain new enclosed areas and I understand he hesitated about going into the trailer when he was moved.
I guess the most frustrating thing to me is that he is better with his owner than with me. If he acted this way with his owner, then I would feel like 'ok it's just the place' but it's not. It's just with me.

I don't agree the horse will stop "testing" you after you do somthing to make him respect you I should know xD I almost gave up on a horse cause of this but she got terrified of somthing and I made her go past it again and again after that she was fine just wait it will end!

Are you both using the same saddle and bridle? If not, maybe your saddle is pinching him.

As a barn owner, I can tell you that most horses need at least a week to acclimate to their new surroundings... sometimes longer. They can be high strung, stubborn... all sorts of different behavioral issues with each independent horse. We see it with nearly every horse that comes in here.

I think the fact that you are less experienced than his owner is making the behavior seem more pronounced. He's testing himself in this new place of his. Try not to get worked up over the horse behaving better for his owner: she has owned him/worked him much more than you have and they know each other. You hit the nail on the head yourself when you said "they have a bond" in your first post.

I bet after a little while longer at this place and you will have your old riding buddy back. Good luck!

Well I had a pretty good lesson on him today. I was skeptical from the moment I went to get him out of the stall and saw he seemed a little more 'high strung' than normal, jumping at little things and such. But I'm figuring him out and getting to know what things I do that 'push his buttons' and getting around that. In any case, I got him to canter on both leads today fairly easily and we even went over a small crossrail. Towards the end of the lesson I could tell he was 'done' and even had a couple instances of him stopping dead and doing the whole backing up thing when I asked him to move forward but he gave in pretty easily when I continued to ask him to move forward. I was thinking about doing lessons only every other week but I think I will do them every week since they are doing BOTH of us good.
Oh, and to answer an earlier question, yes we ride with the same tack. I use hers.