Why do I keep having these dreams please help me.?

In all seriousness I have dreams multiple ones of my boyfriend leaving me for another girl, or being unfaithful with other girls or just in general bad dreams about him. We have a good relationship and I trust him, I just get insecure at times, so insecure it drives me crazy but I try not to show it. I keep having these dreams, this is no lie. It's the honest truth, I've had multiple multiple dreams, please someone help. give me the best advice possible.