I'm going to accuse my girlfriend of cheating
Why would you accuse your girlfriend of cheating?
It is just a hunch right now I have no proof.
If you have no significant proof of cheating, then you should not be accusing your girlfriend of it. You are being unfair towards her by accusing her of behavior that you have no proof of.
Maybe I am projecting
Wow, if you are so unhappy have you talked with her about it? Don't you think she might feel hurt if you accuse her and then cheat behind her back? That sounds really twisted.