Stuck between 2 men

So I have been dating a guy who has been my best friend for over a year now and I do love him... however, my ex who I also dated for over a year about 2 years ago just came back into my life. I ran into him at a party last week and we talked for hours, he explained to me that he hates that we broke up and that he still loves me... I told him I love who I'm dating now but I would like to try and be friends and since then we've hung out and now he's all I can think about. I don't know what to do... I truly love both of them