Sorry to hear about the biting. I don't know your situation but it is a common problem to accidentally reinforce biting. What might work is that you teach your dog a cue like "gentle". Grab a teaspoon and place one of your dog's favorite treats on the end of it with your thumb on it. Present it to your dog and when they go to bite down, their teeth may touch a bit of the spoon, which will cause their mouth to go a little soft, when you get a calm response give your dog the treat by just pushing it into his mouth with your thumb. Do this 10 or so times and when you are getting a calm response every time incorporate a verbal "gentle" before you presnt the treat/spoon. Fade the spoon out so he is just taking treats calmly from you. Use this game with his favorite toys and click and reward every calm response to the gentle cue. He'll get it over time. You could also capture the times he is not biting. Good luck.
