Am I (29f) making a mistake by not getting back together with my ex (42m)

Hi, using a throwaway account because I have some friends who follow my main. I would love to get some clarity if possible. About a year ago, my then boyfriend (42M) broke up with me (29F), because he already has a few kids from a previous marriage and doesn’t want any more. I’ve never really been big on the idea of kids, but I was head over heals for him from the start, it felt so wildly different from any other relationship I’d been in that the idea of a family with this guy actually seemed like something I would want. When he broke up with me, he said he couldn’t be with me if it wasn’t an absolute no as he didn’t want to deprive me of this part of life. It was a classic mistake of not having this conversation at the start of the relationship. I do not fault him for this decision, it is understandably reasonable. He made some mistakes in his marriage and sees the effect it has on his children, and he doesn’t want them to ever feel any less important to him than they are.

I work with him, and while we don’t run into each other every day, we do still see each other often. At the beginning of the breakup, I was honestly devastated, but I tried to be cool about it because we were coworkers. We continued to be silly and prank each other at work, he would text me about things he was dealing with, and I tried to be there for him. Then a weird pattern started where he would be super intense about communication, very flirty and complementary, telling me about stuff he was dealing with, and then he would pull back really hard again. He really was going through a lot after the break up (loss of family members and difficulties with being a divorced Dad), but the ups and downs on how he was talking with me was very confusing and honestly made me so anxious. However, every time he came back, he would tell me how much he misses me, how much he likes me and how he never wants me to leave me, so I would just kind of accept it and do my best to keep him emotionally at arms length within myself. About two months ago, I put my foot down and told him I couldn’t do this anymore, he apologized profusely, owned up to it all, and said that because of past childhood trauma/upbringing, he developed a pretty severe avoidance attachment style, which is what I was seeing. Since then, he’s been more consistent, more low level friend stuff, less flirty, which has been very helpful in terms of my own anxiety, and I really appreciate that he identified the problem and has been consistent about fixing it. However, I’m feeling his absence more than ever now, and i’m wondering if I made a huge mistake. I’ve never felt this way about anyone else, and I have actively tried to see other people over the past year. I’ve dated a few other guys, and have tried to be open to other guys I meet when I’m out but I just keep comparing them to him. He’s so funny, smart, sweet, and I just felt so good when I was with him.

Has anyone else ever been in a similar situation? I’m still not sure about kids, but I know I am not 100% opposed to them. I am wondering if I made a mistake, saying no to a future with someone I really liked for the possibility of a future with children? I have a hard time connecting on a deeper level with others, and I am just concerned I have made a mistake. How do you know if you’ve met “the one”?

TD;DR I feel a strong connection to my ex, but I don’t know if I should try and get back with him or try and find someone else in case I end up wanting kids.