I need help. I dated my boyfriend for over seven years, and was waiting for him to propose once we were done with school. About a year after I was done with graduate school, I flat out asked him what was going on and if he was ever planning on proposing. He told me that he wasn't sure I would make him happy long term because of certain intimacy issues we had. He also told me he was focused on his career and that he wasn't ready to get married anytime soon, which was problematic because his job made it so that we were long distance for the majority of our relationship. None of this was ever communicated or hinted to me before, and I was devastated and heartbroken. I thought, there was nothing more could I do after seven years to convince him to want to marry me, and so I started to mentally check out of the relationship. It took me about three months to finally end things with him.
In the meantime, I'd become good friends with someone new that I met at work. We'd hang out occasionally, but nothing ever happened between us when I was still with my ex (I swear!). After awhile, he confessed to me that he had feelings for me, after which he and I decided to stop hanging out to be fair to both my ex-boyfriend and him. While that may have expedited the process of me breaking up with my ex, it didn't ultimately make me decide to leave him. I left my ex for the reasons above. I started seeing him after my ex and I broke up. Fast forward to the present, co-worker is my new boyfriend.
My problem is, now my ex is telling me that he didn't mean those things he said, and he said them out of fear of growing up and anxiety over our intimacy problems. He says me leaving him was a wake-up call and that he's changed. He tells me I am the love of his life, and that I am perfect, and why can't I forgive him for his immaturity, and the mistakes he made? He doesn't understand why I won't take him back. I don't have the heart to tell him that I'm seeing someone new. As much as he devastated me, I don't want to devastate him. I feel guilty and maybe that I did something wrong by letting myself get close to my co-worker. And even though nothing happened between co-worker and I, I can see why my ex would think I cheated on him (he knew of co-worker before), which would hurt him even more.
I know he has to find out eventually. I was just hoping I could tell him I'm seeing someone new when he was "over" me. I also feel guilty that because I mentally checked out of my previous relationship, it allowed me to fall for someone else so quickly. My question is, when and how should I tell him about my new boyfriend? Was what I did wrong? I just want to do the right thing, which is what I've always tried to do, but I just don't know what that is anymore.