Health Anxiety

So I have really bad anxiety and I always think the worst of things when it comes to me or my family.. idk why it just happens I believe it’s linked to ptsd from stuff that happened in my past. Specifically things such as stds, cancer, etc and it’s caused me great pain to even think those ways but it’s like I can’t control my thoughts about it sometimes.. anyways do you believe that you can think things into existence? I hate that I have certain thoughts and then I bash myself for having those thoughts cause I think they’ll become real.. it causes me Great Depression to know that I could be the reason something happens to myself or another family member cause I’ve thought about something...