What can i do about my boyfriend who won't get help for his ptsd?

You cannot force: someone to get help. You can try meeting with a psychologist to come up with some ways to help get them to meet with a therapist. If nothing else works, you may have to let them know that you cannot continue to see him unless he gets some help.

He has to want it: Your boyfriend has to want therapy and medication, and all you can really do is encourage him to seek both and engage deeply and meaningfully in the therapeutic process. You simply cannot do it for him, much as you'd like to. You can either be his girlfriend or his therapist. You cannot be both, and even though you want to see him get better, trying to be both simply will not work.