So my horse has come along way since march... but now we have this problem with picking up his right lead he just wont to it no matter what I try... he picks up his left lead just fine but not his right lead... need help please....
Before you blame your horse, are you sure you are preparing and asking him correctly? Remember that 99.9% of mistakes are rider error, not the horse's. Sometimes we don't realize that we're asking incorrectly.
How green is this horse? 99.9% of the time a horse will naturally be more comfortable and balanced on one side and they will only want to pick up that one lead. How I get a young horse to pick up the correct lead is to work in a ton of circles. I start them out in a fairly large circle at a trot, then I make sure that I am balanced and cue for the lope. If they pick up the wrong lead, I tighten down the circle to the point where they are uncomfortable (unfortunately, you will be too) and keep them loping. Once they start to get tired, it doesn't take long, they will often change leads to the correct lead. They may crossfire for a few strides or drop down to a trot. If they trot, then just balance up and cue them for the lope again. Once they pick up the correct lead, then let them relax out into the larger circle for a few circles and then slow it back down to the trot or walk and do it again. It is really important to not overdo it because if a horse is not balanced or comfortable on a certain lead, then it is hard on them to work in it for a long period of time. It may take a few days for him to become consistent at picking up the correct lead when you cue for it but when he does, praise him by letting him lope a few strides then drop back to the walk and walk a few circles. The more comfortable and balanced he gets, the longer you can ask him to lope. Don't get impatient or frustrated with him, that is just something that takes time.
I find it helps to put a ground pole down. Start trotting in a circle and have the ground pole right before the circle touches the fence (if your riding in an arena) Otherwise just put the pole where you want your horse to canter from. You can also do this from the ground with a lunge line. Your horse kind of jumps the pole and for the most part they get the right lead. If your sitting correctly and give your horse the right signals. Your voice is also a very good tool, just to get your horse to canter right away when you head over the ground pole.
Like people, horses also have a better side. I have a horse that also doesn't like to pick up the right lead. Like you, I knew it was possible because on the lunge line he picked it up just fine. To teach him under saddle I found that I had to really over exaggerate my cues. On the left lead I barely picked up the rein and pushed with my leg, but on the right no such luck. Not sure how your horse is trained, some people pick up inside rein and drive forward with outside leg and some people do outside rein and leg. If struggling with the lead I would recommend (and this is only temporary until they get it) holding the outside rein just enough (bend neck/hed towards rail) to poke the inside (leg you want them to take off with) forward and then when you get that shoulder/leg moving at that angle or direction, push with our outside leg and they will pick up the right lead because you have intentionally set it up for that to be the most comfortable leg to lead with. As I said, gradually as you practice this it will become so that you don't have to bend the neck towards the rail and the depart should be on the stride you want. Whew! Harder to type than just to show someone.
If he picks the right lead on his own, then your probably interfering as a rider. It still might help to put a ground pole down, but I think you just have to work on your balance and so on. If the horse wants to pick up the right lead (he does it on a lunge line) then your probably just confusing it, or hindering it.