Know the feeling mate, can only say that time is the best healer and to always hold your dignity and maintain your pride. You did the right thing walking out after that, I walked away too and it's something I'll always be proud of myself doing because in the end I was fucked over in a similar situation to yourself, only despite the complete paranoia and suicidal feelings I was experiencing at the time she continued to lie and deny.
As they say, what goes around comes around. You're most likely in for a rough few months, but whatever you do keep yourself in good company and don't go down the self-destructive route. I did and it only delayed me feeling better, now though I feel fantastic (apart from my usual low days/anxiety which is completely normal for me anyway), however at the same time being single has given me time to sit and contemplate why I am this way and improve on it, which has worked and it's given me a lot more confidence in myself that I'd lost by being with that person. Also after so many years it's amazing to be free, go where I want, do what I want, consume what I want, without the constant bitter criticism that was constantly given by her in the last few months, which gave a serious blow to my confidence and sent my anxiety through the roof, compared to the person she was when we first got together. It takes months to realize these things, but eventually you do and it becomes so much better. While they are still tied to the ball and chain...you'll be surprised to see who has the last laugh in a few months time, even if it all feels like shit at the moment.
Avoid opiates, avoid benzos, eat healthy and work on your fitness and you'll have much better sleep and results than any drug can provide. If things get on top of you, I always found weed was an excellent way to let me sit back and realize that things really aren't that bad,but comedowns etc are a tough one. There are plenty more people out there and to be honest I've found some I've been with even far more attractive and better in many ways...
Good luck! And if you feel like shit you'll be surprised how much help a place like BL can be to vent. If you ever want a chat, send me a PM. Be happy to tell you of my experience and remember, don't mug yourself.