The best thing about your diabetes is that with diet and exercise (which you are getting with gym) your diabetes can be reversed.
Not true.
I dealt with a chronic illness as a gymnast which I attempted to hide from my coaches and teammates as much as possible. The time it did come out, it was a hugely embarrassing situation for me, but probably only because I was so self conscious about it already and did not have a very good relationship with my teammates. However, I think it really would have been much to my benefit to be upfront with at least my coaches about the situation. Leaving them totally in the dark just made for some frustrating situations for everyone. They did not know that there would be times I might need special provisions, so sometimes they just thought I was being difficult. After I left the sport and one of my previous coaches really found what was going on she actually got in touch to apologize. My condition was not changed in anyway by physical activity, so in that respect it is very different from yours, but it was embarrassing for me and totally foreign to my teammates. But I really cannot emphasize how important it is to let your coaches know. Especially in a situation where your athletic activity can significantly influence your medical condition.
It is very true that teammates, especially at certain ages, can be cruel, but I don't think you should have too much of a problem in this case, especially if you have already developed a friendship with these teammates. You certainly do not need to tell them, especially if you don't have a close relationship with them already. You really need to discern for yourself what is the best move. But if you do decide to tell them, just let them know it doesn't change who you are or what you are capable of, it's just another step you need to take in your daily life. I'm sure there are resources for teens for Type 1 diabetes and some of them probably include tips on how to discuss the issue with your friends.
Also, doesn't one of the Jonas Brothers have Type 1 diabetes? You could probably use him as a point of reference because he is an immensely successful individual who does everything, and more, that other people his age do.
Best wishes with letting your coaches know and developing a better understand of yourself during this time, more experience will only help you deal better.