Still not sure....

About five months ago I left my fiance because I didn't love the man he turned into he completely changed into someone new, but after I had broken up with him he refused to realize it and I started talking more to my best friend who I now love and he treats me ten times better than my ex. Yet since my ex didn't "officialize"the break up till March, he started telling everyone we knew I cheated on him and lied to him. I did love him...I loved the guy I was with three years ago, just not the guy he is now. And now his whole family hates me and people who I thought were my friends hate me and won't listen to my side of the story. I never cheated on him. I never kissed anyone else while with him, never had sex with anyone while with him. I only started really talking to my best friend a couple months after the break up. I just started dating my best friend, while he's already on his second girlfriend. I want to know how I'm the bad guy in this....and why do I still feel like I did something wrong....