I was in a similar situation years ago. The best thing you could have done was cutting contact with her. It’s hard, but you have no idea how much easier it will make it. Back then I wasn’t mature enough to stop contact with her. The result was that 3 years later I was still hurting for this girl, all the while trying to ignore the fact that she was with someone else (They eventually got married)

The person who I thought was the love of my life left me a month ago. This time I cut communication with her, and while it was hard as hell, you have no idea how much faster you will get over it. After a week I had lost the urge to contact her, and after 2 weeks I did not see her in my future anymore, and didn’t even bother questioning the past. Trust me, I’ve been where you are. Thought about putting a gun to my head. Weekends were a bit rough, I’d picture her going out with other men. You will learn to ignore it and not think about it. Once you accept that she is out of your life for good, the healing starts to happen. Be mad at her when the time comes, you have every right. I personally think it helps.
It does still hurt after a month, you’ll have the odd day where you wake up sad, but it’s mostly sadness from memories, and a little bit of loneliness. Hopelessness is gone. And it’s a hundred times more bearable than before.
Take it one day at a time. The days will pass and before you know it, weeks will pass.