I've been to a number of therapists over the course of my life and each experience was helpful in a different way. I've found that I don't necessarily have to feel like the therapist 'cares' to make progress, although all of them did seem to genuinely care.
I think it does take time to build a relationship with a therapist. It's like getting to know anyone--it doesn't happen instantly. Personally I would give it at least six months before deciding a therapist doesn't care. It could be that they care a lot but it's hard for you to see.
Also, I've found that my recovery has gone in spurts. I'll be in therapy for a few years, rest for a few years, back to therapy for something, rest again, and so on.
Therapy for PTSD can be pretty draining so I think you have to be realistic. It's not like you are going to go to one person for a year and it'll be all better then for the rest of your life. It's something that comes up again and again in different ways, but over time, with the right help, you get better at coping and the illness gets milder and less alarming.
Good luck to you. I hope you decide to make a start. Therapy really can help a lot with PTSD, but it's an ongoing process. You have to get to a place where you accept that this is how your life is, that you need a certain amount of professional support, and that that's OK. You have to feel that you deserve to be happy and feel better, and you do!
(((hugs))))