nightmares 😢

So I was very exhausted because I'm a stay at home mom and full time In college, I did a lot of homework last night so I didn't go to bed until 4am and then our son was really fussy because he has his third tooth coming in. I only got 2 hours of sleep. I went over my parents house and ended up falling asleep. I had the worst nightmare I've ever had. I seen that my fiancée had given up on us, he didn't love me anymore, he did everything that I'm not okay with in a relationship that he knows hurts me and then told me he had found someone else. The dream felt so real, I was only asleep for like an hour tops, and I woke up balling my eyes out and I can't seem to stop. I'm extremely upset and feel so depressed and hurt over this stupid nightmare. My fiancée is at work right now I texted him and told him what happened and he told me that's never going to happen because he loves my way too much to lose me, but I can't shake this feeling on and can't stop crying.. any advice on how to cheer up?