Are they over eachother?

my bf and his ex ended thier relationship about a year ago. Soon after me and him starrted hooking up but him and his ex would still talk...i didn't think much of it because i really didn't care to date him at the time. What i do remember is her being very sad and him just being angry with her all of the time, he wouldn't even want to see her. this was last summer...in the fall she was still calling him once in awhile and texing him....and then me and him started to talk and i asked about her and he said "we decided to be friends....and i started talkin to you sooo yeah". I didn't ask further questions. We casually talked and hung out till about december....then he decided he didn't if he want a girlfriend.... i really think he just wanted to live the single life..so i stopped talking to him i wasn't gunna chase someone that didn't want me. about a month later he started texing me again and suggested to start hanging again..i gave it time...and in january we started again...it got very serious and now he is my boyfriend, he is a great boyfriend but what i'm worried about is his ex. I know that he cheated on her and i told himm that i AM very concerned....he told me that it was a very messed up relationship, and he doesn't like talking about it, but it was a huge mistake and he wants a good relationship with me. Now her on the other had was all depressed about her love life until we started dating she got creepily happy, and mentioned to my friend that shes "soo happy for us". Should i be concerned about ANYTHING??