I had nightmares like that before.
they are very distressing, especially if you are dreaming terrible things involving your child.

I dont think you are losing your mind.
it could be stress, or a developmental stage the child is going thru that (for example) makes you fear losing him, which manifests into a crazy nightmare.

If you have PTSD, the dreams may seem like they are about your child, when really they are just a result of the PTSD.

And i know PTSD can be very hard to deal with.

You can try an antidepressant or something.
sometimes watching news can trigger nightmares.

Maybe try watching something very calm and pleasant before bed each night.
and set up a comforting bedtime routine.