I think my boyfriend is cheating

Shatoya
So me and my bf has been dating on and off for 11yrs. And he's cheated in the past just recently we decided to get back together and lately I'm having this weird feeling maybe he's dealing with somebody else. we haven't been able to have sex for two weeks now because I've been on my period. For the last two days I would catch him in the bathroom kind of like talking low on the phone. What do you ladies think?