Please enrol yourself in therapy. I do not think this can be solved online.

Dr. Shivadev has already given a befitting reply. I hope it helps you. Its true you need to ask yourself if you want this relationship and why do you want it? Forgiveness is Good but tough Talk about it to a mental health professional Consult with me or any psychologist for therapy and counseling online or in person All the best

Hello ! I understand how it feels to be cheated on and it can get truly traumatic, as real as physical pain. However, let me ask you , are you in love with her or the idea of being in love with her. I really appreciate it that you still love her but it can be pathological too like addiction, just because you can't get over the pain of separation ( which by the way can last for few weeks to months and then definitely resolves) you want to drown yourself in alcohol and smokes ? Please understand that she clearly still has front for her ex and she has stated the same for you ? Is it ok if she lies and then continues to have relationship with her ex while still being with you ? Respect her decision and honesty. Think logically , not emotionally. Though I understand it can be difficult when you are down and upset. This is a good opportunity to rethink on this relationship and see the future ahead . Sure it can cause some heartache but nothing which cannot heal.