Muh condolences anon, crappy spot to be in. If you want to know for sure, sit spouse anon down and confront her w/facts you can prove (text) and then state what you suspect. If you're right, body language and reaction should tell you everything.
Anon should remember life is short, if you are unhappy, leave…be happy elsewhere. No reason to torture yourself day in/out.
Muh $.02