I have a 4 yo Arab/quarter gelding. He came to me very green and we sent him to a trainer for 90 days. Previously, I was working with another trainer who was supervising me riding him , but he bucked me off so many times, that she recommended we send him to this guy and start over. The trainer did not do any follow up with us and I only got to see him work him one time in the 90 days. Now that he is home, he is better, not bucking again yet and we have had some lunging problems. When the trainer sent him home, he said to lunge him for 30 minutes and then ride him at a walk and trot. While lunging, he initially started stopping and turning towards me and I would just go to him and start him over but that eventually turned into striking at me so I used the whip on him once and that seems to have solved that problem.
We have gone on a couple of short trail rides at a walk only, and he is pretty good as long as he is following my husbands horse, he won't go if I ask him to lead the way. He seems very insecure and he spooks more now than he did previously.
So, i decided to try having him go on his own in our arena and that went pretty well and I was even able to get him to trot a little bit, but he is now tossing his head a lot and keeps trying to take the bit and put his head down. It's not a fast tossing, if that makes sense, more like he is trying to get his head away from me? He is so focused on this that he stumbles at times from not paying attention and I feel like I have to hold him up. the bit is a dutton colt bit, tear drop style tom thumb. I had a regular snaffle on him, but he played with that one even worse. He is also still refusing to go but not terribly so, I can get him to move with leg pressure most times. It takes a lot to get him into a trot and that is when he really starts the head stuff and acts up. I think he is going to explode soon.
Can anyone offer some advice or insight into this head movement? I have a call into the trainer, but frankly he has not been much help and I don't even know what he really did with him. I love this horse and put a lot of money into him. I just want to do things right by him. I have some experience, rode a lot as a young girl and even jumped and barrel raced, but it has been some years and I don't bounce as good anymore on the ground.
Any advice is appreciated.

~Lorna