Still in love with ex

Me and my ex broke up last August. We were together for 2 years, the longest I've ever had. I love him so much but he treated me like crap. He always put his friends first an yesterday he messaged me claiming I was flirting with his friend who's 1. 3 years younger than me and 2. Has a girlfriend! And I wasn't flirting with him but he got mad AT ME! Because he was his friend! He claims he still loves me but obviously not. I have met a new guy who I have been talking to for MONTHS like almost a year now, but I'm scared to get with him because of my ex. I'm just afraid that it's not fair to him or something. Me and my ex no longer talk and we haven't until he decided to tell at me. I don't know what to do anymore. What would you do in my situation?