SOS help me please!!

Okay girls, I was sexually assaulted in my past and he took my virginity and I came and since then i have been afraid to come when I have sex so I stop and calm myself down when I get close and my boyfriend knows of the incident just doesn't know why I'm scared and everytime I don't cum he feels unaccomplished but he says some little things that trigger me like "there's nothing to be scared of, you cum when it's good sex" and I started crying because of the "good sex" part and he was confused and I don't know wether to tell him why I'm scared or just let it go and try to get over it..