I met a wonderful man five years ago. A year into our relationship he said he had previously a problem with cocaine. I was utterly naive and didn't know what this meant. Two years on we moved in
I cannot imagine how bruised you must feel. Your world has been shattered on many levels. Someone you loved lied to you, changed his behaviour and then left your shared life without a word. The wonderful man you met, turned out to be someone completely different. Your loss is big and I suspect you will go through the various stages of grief which are (in no particular order) shock, denial, anger, bargaining, sadness and acceptance. There is no magic wand to heal the bruising, but knowing about the stages of grief might help you understand that what you are experiencing is normal.
I am thinking the best place for you to start is perhaps 'self-soothing'. We have neurological systems in our bodies that help regulate our emotions. One is a 'self-soothing' system that helps reduce stress levels in our bodies by increasing oxytocin and vasopressin. This system is activated by kindness, love, sex, close relationships (family, friends, partners) and meditation. The more compassionate you can be towards yourself the more you get to repair your bruising. This includes doing nice things for your self, getting a massage, spending quality time with friends and family and whatever else you find relaxing and kind.
The second thing I would recommend is 'go with the flow' of your emotions. Sometimes if we fight our emotions we end up making them worse and intensifying them. We may start creating behaviours to stop them, for example smoking, drinking or eating more, leading potentially to a myriad of other issues. Poor health, self-loathing and so on. However emotions have a habit of dying down like a wave, and if you can somehow ride the wave, you will fair better in the long run.
Finally I wonder whether thinking about creating a new future would help. When you feel ready to, engage in things that would create a 'new you'. Go to therapy, take up a new hobby, learn a language, to the gym, have a new hair cut, take a hiking holiday , whatever, but something that develops you in some way. I know at this point it might be easier said than done, but engaging your brain in other things helps you move forward. For now, it's probably very much about taking one day at a time. I think you have done the right thing to reach out, perhaps also talking to someone will help too.
I wish you the best of luck.