I have been in gymnastics now for about 6 months, I'm 19 and I'm starting to gain a little bit of back flexibility, but not enough. Right now I do bridges every night but it isn't near enough still. Is there any other stretches or exercises I could do to gain more flexibility in my back required for tumbling?

I don't know any excercises, but you might want to try Hylaronic Acid. I buy mine at Wal Mart
In the vitamin aisle. If I didn't take it I swear I would be as stiff as a board.

Being a gymnast myself, I am very flexable and I find the harder I try and the more I want something in gym the easier I get it so I would suggest to keep stretching your back and keep doing those bridges and in time you will notice that you have become more flexable... hope this helps!!

I have been doing bridges every night or at least 6 days out of the week am noticing some imporvment over the 1.5 years I've been doing it. It is just taking forever lol.