Stupid dreams 😩

So, I've been with my boyfriend almost three months now. We started out as friends and completely fell head over heels for eachother and started dating. Since we've been together I've dreamed of him cheating on me almost every night and I wake up in tears and sweating horribly.. Sometimes wanting to kill him. Haha. When I tell him about my dreams he tells me to stop it because he would never hurt me in any way. What does this mean? Or could it be my insecurities from my past relationships?