I just can't get over a past mistake and keep having regrets. How can I better cope?

It's been 10 yrs, but this experience has marked me. I still even dream about the person. You see, I had an illegitimate relationship with this man, which produced a child that I love beyond words. The relationship had to end and I still think of this person after all these years. It hurts. I feel as though I'm not healed, even though I went to confession (I'm Catholic). I want to do better next time around by not having sex until marriage. Anyway, can someone tell me how I can cope with this? I keep putting myself down. No rude comments, please.