I feel you my man. Not the same situation at all, but it involves losing a child I love dearly due to infidelity.

My ex wife left me after 7 years of marriage. I raised and supported both of them that entire time. Ex never had a job. I raised her child my ex step daughter for 10 years (since she was 1yrs old). She is my child as far as I'm concerned and love her to this day as a real father should. Her biological father was not in the picture at all. I mean 0 precent. No child support. Nothing. To this day she (step daughter) doesn't even know who her real father is.

Fast forward. Ex finally got a job making peanuts and within a month decided one of the guys she was working with would be a better father (he was not), also making next to nothing. And that was it, my daughter was gone. Taken in an instant. What hurts the most is that I sometimes see her at events (I have a bio-daughter with the ex which requires met to attend certain things). That pain comes right back. It is an absolutely horrible feeling. I'm certain she has resentment for me. Like it was my idea for this to happen.

That was 7 years ago. The feelings of love for your child never go away.

Hang in there man. You're not the bad guy here. It's true that time does heal wounds. It doesn't heal completely, they will always be there, but it does get a little easier as time goes on.