I need advice seriously bad.

so, my fiance and me are planning to be married in 2 weeks. well, I have my suspicions. so he goes to class from 9-1 but he's always staying after for "20 minutes" there's time he doesn't talk to me, he's always doing things that require him not being on his phone. he lives with a girl. he tells me he will never cheat on me. but I have a hard time believing it. I'm constantly accusing him of lying and cheating. idk what to do 😧😧