I think before jumping with him, you should check everything is ok on flat work. Be sure your horse has a good pace, understands and answers to your demands, that direction and control are ok... If so, you can start working on ground poles and check again transitions, direction, control are ok. Then you can start jumping small obstacles.
It is a good idea to start working in liberty to see the horse's behaviour. If everything is ok in liberty, you can start over. Put two small obstacles when you lunge him. When he crosses them correctly, do the same thing but with you on his back. Do not hesitate to work in trot at the beginning, or even in walk if necessary. When it is ok, you go to the next step (higher and more obstacles, then canter...). Good luck, be patient!
Lunge your horse and make him jump, so you will see if he also charges when you're not on his back. If he does, your horse can have a back pain, call an osteopath!