is he cheating?

Okay so my boyfriend of nearly 6 months and I have been an item for about a year but it took us ages to get together because people hated me , expecially he's friends . Anyway he's been acting strange recently , taking ages to reply and that not telling me where he is? Whenever he's at home he never texts me back he always snapchats me instead because it's "easier" but whenever we're around he completely avoids it and once I saw a girls name pop up saying she was trying and he quickly locked he's phone and put it down? Am I the only one that finds this suspicious? Also he always jokes about going to meet he's " other bitches" when I think there's some truth In this joke . Am I just overthinking or are these warning signs ?