Tell me what the ultimate payback is for this?

I was dating a girl and she got pregnant by someone else while we were dating. she told me about the other guy once she found out she was pregnant, but she insisted that by her conception calender I was the father. This would have been my first one-a son.Imagine how happy I was. I work everyday to make sure he or any of her other 3 kids want for anything. I did more than the other guy in terms of being there for her and all that good stuff. The Kid was born he didnt look like me but I didnt say what I felt I just thought oh well he will get darker and then I will be able to see me in him......wrong wrong wrong he looked nothing like me nor anyone in my family so I got dna test right before christmas got results back kid not mine..(hurt beyond all imagination). she told me the dna test was wrong and had her grandma call me saying the same damn thing like I am some kid or some ****. I didnt appreciate that as I am a grown azz man....I bonded with the kid a little and she took it and ran with it so I made her go test the other guy and he took the test but didnt show up to get results. Turns out the kid is his and now becuase she did some stuff one night costed her a really good man. I like the girl, but I dont wanna take care of her and 4 kids and me. I am ballin, but not like that though. I wanna get back at her and make her feel the same hurt as i did. could someone please tell me how to make her hurt like she did to me. I think she was being selfish and only thinking she got a good man who will work and I cant loose him, but I will not take care of a kid that was born from a cheatin azz manipulative b888h who I feel is playing me. I want to emotionally hurt her could someone please help with some advice.