My ex told me he wants me back

In October I started dating this guy that was older then me , he’s 17 and I was 15 , we dated for like 3 months then broke up . When we were dating he said i was really emotional and he didn’t know how to handle my emotion so he wanted to break up so we did . Now I’ve been dating this other guy for 2 months , almost 3, and I’m really happy . Me and my ex are still friends and hangout bc we have the same friend group . Recently he told me he wanted to talk to me and he said he misses me and regrets breaking up and said he felt like he wasn’t trying hard enough to keep me . I don’t know how to feel , i think about him all of the time and I love him still bc he was like my first love . But I love my boyfriend too , he treats me so good and makes me so happy . I miss my ex a lot but I can’t do that to my boyfriend , my ex said he would wait for me but I just feel so sad and guilty that I miss him and kind of want him back .