The guy I love has a girlfriend what do I do?

So there is this guy I am in love with and have been for 2 years. We started dating last August and broke up in February or March. Well I am still 100% in love with him and he told me he still loved me right before he started dating another girl now every time I see him with her or see our pictures it makes me want to cry. I started dating a different guy to try and get over my old boyfriend. I thought I was starting to love the new guy and we went out for awhile and we were really good friends before we started dating. I just dont know what to do about Ethan....(the guy I am 100% in love with) I dont like ruining peoples relationships but if I have to I will.