Dude this isn't healthy for you. Meet other women. Hell, even make some male friends and hang out with them. Maybe you have friends but the way you're acting here (no offence) you don't have any. I was in a 3 year relationship and we broke up (and it wasn't my choice) which was obviously gutting. I no contacted for a couple weeks, spent all my free time relaxing (enjoying my favourite shows, going out and meeting people, hanging out with friends) and after that I had moved on, we're even able to talk once every few weeks as friends, to see how each other are doing.
This sh!t mental state is only lasting as long as you let it. You need to start focusing on yourself. What I found helped me move on very quickly was by seeing what my future is, almost like a new timeline. eg, I'll hang out with friends, go to the gym, ace my studies, get the job that I want at the end of it and have a fantastic time working my way up the ranks, meeting new awesome people (because they're all out there) and everything. Looking at it that way, it made everything before that point seem like it wouldn't have any sway on that future. You just got to see yourself as a desirable person with a bright future ahead of you. Then you'll see that cutting this girl out of your life (at least until you're ready to make it a casual friendship) is no biggie.
Stop dragging yourself down with noone will ever want me, I will never want anyone except this girl and I'm so depressed etc etc. You'll believe it as long as you tell yourself to believe it.