I also have ptsd from sexual abuse, I know therapy seems pointless but it can really help, and sometimes antidepressants can cause more vivid nightmares. I struggle with nightmares as well and what usually works is doing something before bed that’s guaranteed to put you in a good mood, eat your favorite food or listen to a favorite song, talk to your favorite person, etc. Frequent exercise can help with insomnia but if that isn’t your thing maybe meditation or asmr. Try avoiding your triggers until you can face them, it took me a few years to get over the bad ones so don’t worry about how long it will take, your body knows best.

Therapy is absolutely saving my life. Finding a good therapist can be hard though. I highly recommend one who does EMDR - it's helped massively with my CPTSD. For nightmares, I've always tried to spend time meditating after I wake up, reminding myself that it wasn't real, that it's over, and that it's not going to happen. Especially when I dream about my abusers, I remind myself they're out of my life and I'm safe now.