Thanks, and sorry yeah, I could see how that might be confusing. I guess I'm just worried that I might be over-thinking things since I don't have concrete proof for anything he's done, and I'm not sure if I should talk to the girl or not. (Like maybe there are things I'm not thinking about when considering this?) I also worry that I can't trust my own judgment (see #1 below) so having outside validation helps.
There were a lot of reasons for our past break ups, but they mostly boil down to:
1) I've tested positive for an incurable neurodegenerative disorder which leaves me with about 15 - 20 more years of life. In the past, I felt guilty for being in a relationship when I felt like he didn't really understand what it would mean for him. I still don't think he fully does which is why I think I'd be happy for him if he did somehow find someone who could be supportive of him if/when I'm gone, morbid as that sounds.
In light of that, it's always seemed silly to worry about small things like this, but now I am questioning if maybe I should take these things more seriously since they do indicate some unhealthy behaviors in a relationship(?).
2) At one point, early on in our relationship, he told me he had feelings for another girl and asked if he could ask her out. I was interested in a few other guys at the time so I suggested we take a break to experiment with other people. Neither of our interests panned out so we got back together a few months later, but then we took another break like that a year later.
3) We lived together for a while and realized our living habits were pretty different (he's very messy and used to eat all of my food without replacing anything, rarely contributed to cleaning, etc.). He's since gotten a lot better about those things but since we live in different houses now it's easier. He also used to be bad about reciprocating things and I got frustrated at him a few times. It felt like I would watch 3-5 movies that he liked but he wouldn't watch one that I liked. Every time I suggested something he'd override my opinions but then later responded to my pointing this out that I, "never expressed any opinions," which is why he felt like he always had to decide what to do. I felt like I was losing my personality to his and, I think, I still sort of feel that way, but we've been working through that recently, too. I don't think he did it in purpose, I genuinely think he wasn't aware of it(?) but he's also the first person I've ever run into this so strongly with before.