I'm having problems and I don't know what to do

This is kind of a long story. All names are made up.

So everything began when I was 18. I had to move out of town for college. A few of my friends on the friend group came to the same town, but most didn't. To this day, I only see some of the other friends from the group on holidays, and even that is not lilely to happen.

At that time, me and my friends would see each other really often, basically any time we could. And we would mostly be and my friend Chris' apartment. It had a really nice view and balcony, to smoke and drink, and it was only us, no parents at all, so some pretty wild shit happened.

One day, Chris, Ethan and I were going to a college party, we were all obviously from the same college, and all from the friend group. Chris told us to go to his apartment to drink before going to the party, and both Chris and Ethan said they would bring some people, and I felt ashamed because I basically had not any friends yet. So, when I got in the apartment, Chris introduced me to Daniel, and Gary, and Ethan would introduce me to Bob. So we went to the party and it was all good, I had a pretty good time, and I was some time with Ethan and Bob, but mostly with the others. That night I had my best experience with weed than before in my town. Some hours later, we got to Chris' and I think that night we stayed up with Chris and hid friends, talking, drinking and smoking. After that, we all added each other in social media. A few days later, Daniel DMs me to invite me to something at Chris'. The day I went, Daniel introduced me to Mike, and from then, I began smoking weed a little often with them.

But I was doing really bad at college. I began gaining weight, smoking tobacco and barely even sleeping for insomnia. I had basically no friends and was just not feeling well. After some months, I talked to my mom to see some professionals and after some time, I was diagnosed with depression, I don't really want to talk about it to be honest. I took a break from my studies and kept going to Chris', I would smoke some weed here and then, but would mostly drink, really a lot.

Six months later, after coming back from my hometown, I began smoking weed or eating edibles by my own. I even tried mushrooms. It was not really often, but it was still worth to mention, because of my diagnosis, I kind of did it to escape from my depression.

Some more others months later, I was still being medicated (I am to this day), I changed colleges, and was not diagnosed anymore. There I made my friend Travis and would always see him in classes, since we shared the same ones. We would do all together, would eat together, would go out to smoke tobacco and stuff. But at the same time, I felt like Chris would barely even invite me to his place anymore, so I wouldn't either see him or his friends anymore, since I changed college. At this time, I was not smoking weed at all. Only tobacco, and not drinking as much.

After all this, I didn't really saw any of my friends from the group and would only see them on holidays. That was kept to this day.

I was diagnosed with depression again, now even worse. I began self harming myself a few times, for some really deep personal reasons, even went for two unalive attempts with my medication, but I convinced everyone the second one was a desperate attempt to get asleep, but I would always tell my professionals about the rest of the stuff. To this day, I don't know how I have not been taken to the hospital not even once.

I made a girlfriend. She has really helped me in all of this. Spending some days of the week at her place really helps me, but at the times I'm at my home, I have always smoked weed for like the past three months. I have told my professionals, but I think they don't really take it seriously, but I'm worried. Because I quit smoking weed because I felt it didn't do good to my mental health. And now I am, I'm smoking a lot of weed a week, and I'm in an even worse depression.

I think I want to quit, but I don't know how. It scares me, I don't know why. And at the same time I don't want to. I don't know if I should tell my girlfriend. I have bought more weed than ever, spending like 1/4 of money. I'm doing horribly on college and not seeing any of my friends, since Travis had left that college.

I don't know what to do.