Boyfriend

I checked this ask. Cause we've had some problems. Apparently he dated her. Idk what to do. So scared. Anyone think he could be cheating? I've been dating him for 3 months.please help... 
Background. When we first started taking he was still flirting on ask. When we started dated he promised to stop. Yesterday. I found out he was still on it. I got pisseed and upset. Then this chick posts this. And I got scared. He's talked to girls before and "forgot" to tell me. So idk I'm really worried and scared. 
Really need someone to talk to.