Bad dreams

Im 23 weeks pregnant and i keep having bad dreams about my boyfriend.... this happened two times already i wake up mad. My dreams always involve another girl. Like he’s cheating on me or something but i know its just a dream because I don’t think he’d ever hurt me like that... & I have told him about it “ he says baby really ? U kno ill never do that to you” is there a reason why this happens to me 😢