Thanks so much everyone for your feedback! I understand some of this is typical young horse behavior. I remain calm and am trying to simply find that balance of reasonable expectations and continuing to move forward. We don't drill on exercises as I try to keep it interesting. He's a smart horse so I try to be sure to keep his attention and enjoyable for him too. Additionally, there's no denying that I'm new at this and have only had my own horse for 3 years. I do my best in terms of feel and always release pressure at the slightest try or improvement. Since I'm a novice, I also have a trainer that I worked with on my last mare and still continue lessons as needed with my new gelding. Here are some additional questions :)
I agree with what has been said, and as Sorrel3 specifically mentioned, time and consistency should help your problem. However, for flexing of the rib cage, bending circles will help. The softer your horse is with lateral flexion, the easier circles will be. Choose a direction and circle the horse, maintaining forward motion. Bend their head by lifting the inside rein to your hip. Press with your inside leg in the center of their barrel to encourage the rib cage to move out, and use your outside leg to keep their shoulders from dropping if needed. After the horse gives his nose towards your foot, and is moving forward, release the pressure on both the reins and through your legs. Be sure to completely restart the procedure in the opposite direction. If the horse is struggling to maintain a forward motion, ask for less bend in the beginning. Resistance through the mouth is often a result of a stiff body; therefore, bending through the midsection will encourage the horse to soften through their head.
I tried circling him and he gets cranky so I try to do a few circles, do something else, then come back and circle again, etc. I notice when I release the pressure, he goes back in the direction he wishes. Also, how do I know if he's dropping his shoulder?
I think this is a good point. Though your horse cannot be allowed to pull you all over the place, it is worth considering that the horse is not suddenly becoming stiff becuase he's stiff. He is probably becoming mentally resistance due to his frame of mind.
Maybe, you are boring him and he see's no purpose or reward for doing what you ask. Maybe you are leaning on his mouth, maybe you are endlessly bending his head around, or maybe you're asking too much of a young horse. I really couldn't say . But try to find places for him to be successful. If you are asking for him to give to the rein, if he does give, give him a good reward and maybe quit. Don't do it over and over again.
Too many people haul the horse's head around to their knee, while he's standing still, over and over again. The horse never really softens to bit nor connects that to any kind of bend in his body, he just allows you to haul his head around real far while his body stays stiff as a board. And having his nose on your knee means nothing if the head is all twisted to the side and rolled over in order to reach there and he's forced to lean way forward on his front legs. When people haul the head around, against the horse's resistance, you end up deadening his response the rein in his mouth and you "break" the body in half because the rein no longer connects to the hind end. So, like a semi truck cab can turn hard one direction and the whole body of the truck keep going forward, you break the head and neck off of the hind end and lose control of the whole horse.
Horses that are ridden this way end up having "rubber" necks. You put on a bit of rein and they just come around to the side, avoiding the rein, and run right through the shoulder.
We were making good progress with him pulling on me and softening. I try to be as light as possible, and am trying to teach him I only ask with an ounce of pressure first. However, our last 2 rides weren't so successful. It was cold and I was trying to find his places to be successful but I did feel a bit discouraged. While I don't drill on these exercises as mentioned above, he's already trying to bend around as soon as we stop or I try to tip his nose in for a circle. I suspect he's trying to be evasive as he doesn't love to circle and I know is common. I have no illusions that he's heavy on the forehand and really needs to learn to use his hindquarters. Any suggestions?