If you've been traumatized or had a rough past, its not just about "forgetting the past". Actually, the core of PTSD is not being able to move past the things that have happened to you.....hence why its a "disorder".....that is, if it was as easy as just forgetting the past, we wouldn't have a disorder! I don't know if you have PTSD, but it sounds like you do have symptoms as you mention flashbacks.

Maybe you should find a therapist and stick to talking to the therapist about your struggles? It can be a lot to put your personal struggles onto friends and family members. I used to talk about my PTSD a LOT, but then someone told me to STFU (in a nice way, LOL) because I talked about it all the time. It hurt to hear this, but he was right. I had made the disorder my identity and knew I had to move forward and stop talking about it with my friends and family.

Is thinking about the past in your control? Nope, not if you deal with intrusive thoughts and flashbacks. You can learn coping skills in order to minimize flashbacks and how to recover faster when you do have them.