I think my aunt slept with my boyfriend
That is quite an assumption, why do you think your aunt has slept with your boyfriend?
I get so many hints from them being so close with me.
You should be sure this is the case before you bring it up. It would be bad to accuse a family member of sleeping with your boyfriend.
I know what I'm talking about.
If you are absolutely positive that your aunt is sleeping with your boyfriend, then it would be best to confront them both and immediately break up with him. You deserve to be treated better and should let them both know of how they betrayed your trust.