Should I tell her?

About 2 years ago I was seeing this guys and got pregnant. I had an abortion. One thing led to another and we stopped talking and then a little later he started dating someone new and they moved in together. Anyways a couple months ago he contacted me and I asked him about his girlfriend and he said they weren’t seeing eachother anymore and that he moved back home to take care of his mom because she got cancer. He came over a few times since then and we’ve hooked up then he tells me he actually still lives with his girlfriend and they’re still together and he just wanted to focus on something else until his mom passed away and now that she passed he wants to focus on his girlfriend. I feel so used. He did us both so wrong. The only reason I didn’t jump on telling her yet is because I know she has a lot of depression and self harm issues. I don’t know if I should tell her or just let it go and let him live happily ever after and she just never know about his lying cheating ass.