Boyfriend has no trust

Lauren
I've been in a relationship with my boyfriend for 3 years. I love him and don't want to be with anyone else. I honestly want to be with him forever and see us having a happy future together. I'm in no way interested in anyone else. Last night I went out with friends and he was clearly unhappy about it. Accused me of cheating on him and has been off with me all day. I haven't done anything to seem untrustworthy. I love the guy. I care for him. Id die for him if I had to. Just feel so hurt that he doesn't feel like he can trust me. I've never cheated or even flirted with a guy since the day and hour we met. Don't know how to make him realise I'm serious about us!