20 years old and super depressed after a lot happened this year. I feel completely different and I am about to fail out of college and I have so many questions and worries and just want to vent everything.

Might be a long post. So basically I was very shy and reserved in high school. Pretty anxious and depressed and lived inside my own head 24/7. I constantly felt like people were watching my life through my own eyes throughout my high school years. I also constantly lived in fake scenarios with fake characters I created in me head. I would love to hike for hours alone just imagining.   
First year of college was great for me. I made great friends and really connected with the community and felt seen for the first time. My mental health was at an all time high and I was working out daily, almost to 185 lbs and muscular frame, practicing my jazz saxophone for 1 hour daily, waking up, 4.0 GPA and engaging with the community.   
Over the summer, I had a situation with a girl where three days later she accused me of SA in a public way. It wasn’t criminal (Because it actually wasn’t), but she told me she had problems with this/intimacy even before we started dating. On top of the heartbreak (she was my first love), I also felt intense guilt where I couldn’t eat for 3 days, loss of friends and status and intense anxiety about people gossiping about me (also very introverted), and the whole situation was out of control. I ended up walking 55k steps a day for a week straight and scratching myself until I scarred. My parents saw this and got very worried and it was hard watching them go through that with me. I know it was an overreaction to just losing a relationship and college community, but I suffered from anxiety, depression and whatever weird thought patterns I have for my entire life, and this whole situation just was a huge trigger. I also started smoking weed heavily. This caused me to dissociate more and my parents think I’m a drug addict.   
I worked a maintenance job and also moved to Montana to work at a ski resort but I really wasn’t present the entire time. No thoughts about myself, my future, my hobbies or positivity for the past year. For some reason after this I lost my entire conscious frame of how I lived, no longer am I interested in learning, self improvement, music or working out. For the past year I’ve just woken up and gotten through the day. There’s no excitement for myself or my future. I used to think about the previous situation with the college and the girl an insane amount (like every single  thing I did was just a distraction to stop thinking about it) for months. The first night it happened I stayed up all night with a pit in my stomach suffering. That same feeling still comes and overwhelms me even though the situation is resolved.   
I was always self-confident (but shy) but I was able to talk to people and not worry about what they thought of me. Now I am hyper aware of it and feel like everyone hates my presence. I haven’t read a book, watched a movie, show or really committed to  anything. I just have a phone and weed addiction. I also recently tried MDMA, Xanax and Adderall which I found at my new college. I will stop these.   
I don’t even possess an interest in my studies at my new school. And I feel shame for going to class etc after missing it. I am failing 2/3 classes with below 40%’s. I really don’t know how I let myself get to this state.   
Anyone know how I can get my old self back? It feels so foreign to me. I wake up and feel fatigued throughout the entire day. In fact I don’t enjoy waking up. I know that the incident wasn’t huge and there’s no danger in my life right now, but it really spiraled with the drugs and bad habits. I just hope I’m not permanently gone. Can someone help me process this?