Need advise on my young horse, please help?

It was probably an off day or a learning stage. I've found that at 3-4 a young horse needs security and they tend to do just what you ask them etc. Once they get to about 5 they then start to question your authority and have a few spells. ; ) I'm guess his age has a lot to do with it. I'd keep going a bit more and see how he is, if it's not safe for you to ride then have someone else hop on him and see how he is. If he is going through a stage it may be better for you to have someone else school him for you for a bit in order to keep your back in good order. He'll probably come right though, and it may be that he has an occasional day like this until he grows up some more.