I feel Miserable TW: mentions of Abuse, PTSD, Depression, and relationship problems

I can't seem to stop thinking about the bad things that have happened to me and reliving them. It feels like these memories and the people that hurt me are haunting me and I can't seem to focus on the present almost at all. It's making it so that I can't feel joy from the things that I love, I think I'm entering an episode of severe depression because of it. I'm struggling to function and can't sleep more than a few hours at a time, I'm struggling to study and do assignments for my college classes more than before I'm nearly failing one class despite being on the Dean's list because of my grades.

I've been isolating from my partner unintentionally because I'm trying to hide how I'm feeling,  just because I don't know how to communicate it to them. My partner is struggling right now too, and I've been focusing on trying to help and support them because it's easier for me. I'm to a point where I really need support and help, but I don't know how to ask for it or communicate what I need. It feels like my partner hasn't been very present when I do attempt to talk about things, and I can't really get their undivided attention a lot of the time. I've brought this up, but it's still been happening. What i'm experiencing, as well as my partner not being present when I need it is affecting my ability to communicate. 

The trauma I've been reliving is from my childhood up until 2-3 years ago. I'm in a better situation now, but I have no idea how to work through this, it's very intrusive and affects my ability to live in the present moment or be productive, and even do things I enjoy when I have time. I've had a life riddled with abuse and neglect from family, homelessness, bullying, as well as being hurt and attacked by people I didn't know among other things. I don't know how to feel safe, I only know how to survive and that makes it so much easier for everything to catch up to me. I have no idea what to do, and I feel like I can't go to friends either because they won't understand and I don't trust them enough. I know a lot of it is just my anxiety, and I know that I CAN go to my partner, I just don't know how to get through the mental barriers to feel safe and comfortable enough to really try.