Hello Oj1234, it would be a wonderful thing if we could flick a switch when we leave a relationship and erase all the hurt that happened. I would try not to be too hard on yourself that the after effects of this relationship are still being felt a year later. It sounds as though for signficiant portions of the three years you were together, that you were in a heightened state of anxiety, walking on eggshells, not knowing if you were going to be praised one minute and condemned the next. Couples argue, of course, but when it gets personal those remarks can cut deep for years. And to cap things off with losing a child, having your fitness as a father questioned, and infidelity.
I can understand you would feel exhausted after several years oft his, particualrly when you cared deeply for her and put everything you could into the relationship. Perhaps you feel like despite your best efforts, you weren't good enough. Perhaps you're terrified of this happening again in your next relationship, or perhaps you're worried about ever finding someone else again. These are all perfectly normal things to be feeling after you've been through.
What strategies can help? I would suggest trying to find passion again in what fulfils you. Your post describes a lot of your efforts in trying to please her. What things make you feel happy? What people do you have in your life to spend time with that enjoy your company and make you feel wanted and valued? What makes you laugh? What activities do you get so absorbed in that you forget what time of day it is and just be? Move towards all of these things, even though sometimes the motivation isn't there and it feels like work. Keep pushing through and eventually the hurt will begin to fade.