You both have gone through a lot, that seriously does suck and by reading the posts I can see the pain. Brownie for you, you seem like your still stuck on her as much as you deny it. You need to face this problem, observe your reaction and check with yourself, is it your brain that just wants the satisfaction of being comfortable so that you are not alone again? Part of the reason for this is because of the fact that she "kind of cheated on you" it makes you feel unjustified as to why she did it which breaks the heart. You mentioned that you miss the relationship but not her, you answered your own question. When you stated that you can't get yourself back, now thats your brain talking and saying your depressed, that second voice in the back of your mind verifying everything you say, hear and read is what makes you depressed. But you can turn that around by keeping your head up, do some sport, do something you love, read books and learn from what has happened. But who isn't alone in the world? Being alone is what helps you to discover more about yourself and do the things you enjoy in the world.
THE NUMBER ONE THING FOR BOTH OF YOU RIGHT NOW IS YOUR HEALTH! I strongly RECOMMEND taking up TAI CHI to improve the testosterone levels, strengthening in the bones, muscles, co-ordination, increase of new brain cells by learning how to use the body and create the flexibility of joints and muscles.
What you want sometimes may be your brain only seeking the comfort and satisfaction. But what you really want to do with your gut feeling, instinct and heart is reality.