I quite sympathize with you and understand how you feel. To help you save your friendship, here is my advice.
To begin with, having been friends with him for so many years, you should trust him. Maybe something happened to him or his family. He probably doesn't want you to get involved in it. So it may be a good idea to give him some time to be alone. Finally, you can ask another friend to help find out the reason, which is the key to solving the problem.
I hope these suggestions are helpful and that you and Tom are on good terms as before.