Im in love with my ex... ((Complicated situation for me.))?

Okay, So Kevin is my EX boyfriend and Stacy is a very close friend. Back when me and Kevin were dating about 2 weeks into our relationship he cheated on me with Stacy. ((We only dated for 2 weeks and 2 days)) I found out from his best friend. At first I didn't care and was just going to let this slide.. Stacy texted me and told me she was in love with Kevin and couldn't stop thinking about him. I love Stacy so I wanted her to be happy. I broke up with Kevin so they could date. Eventually they did. They have been together for like 3 months and this whole situation is killing me. I absoluetly love him and so does Stacy. The cheating situation tore me and Kevin apart and brought me and Stacy A LOT closer. <\3 Help?