What should I do with my Ex boyfriend?

Me and my ex broke up almost two years ago on good terms because he was completely honest with me on how he wasn’t ready to be in a relationship even though he thinks I’m perfect. He told me he just couldn’t hurt me anymore and we are better off just being friends. I’m 22 now and he’s 26 I have a new boyfriend that’s 23 and he would do anything for me and he’s always around. I been with him for nine months now and now my ex can’t resist me. He is always telling me how much he loves me and how beautiful I am to him. I’m still in love with my ex but I’m happy with my new boyfriend. My ex knows about my boyfriend but now I feel he’s trying harder to be closer to me now than before as if he wants me back. He’s been this way since the begginning of my new relationship and he’s not giving up. I care about him but I know I wouldn’t be able to trust him. He more of a better friend than someone to have a relationship with. I’m still young and need more experience so should I keep him around as only a friend or have him as a sidepiece?