Gut feeling he's cheating

Megan

This might make me sound crazy but I really have no one to talk to. So my boyfriend and I have been together just about 3 and a half years. In the beginning I had some insecurities because I had been previously cheated on but since we've been together I really have never even considered my boyfriend would cheat on me. But over the past couple months I can't shake the feeling that there's something up. He's been snap chatting and Instagraming other girls and I'm not the type to tell him he can't have friends that are girls because a lot of my friends are guys, but the nature of their conversations seem a little too friendly. Also he won't leave his phone near me anymore and he always makes up some lame excuse as to why he goes into other rooms to 'play' on his phone. Of course I've talked to him about my concerns and he tells me they're just his friends but I'm not sure why he would just now be talking to them since I haven't heard about them over the years. He's just been acting really shady lately. My last relationship was both physically and mentally abusive and I try to be the best girlfriend I can be. I really don't know what I'd do if he is cheating it took me so long to trust again. Do you ladies think I'm just being crazy?