[Advice] 4 year relationship has turned into a roller coaster of conflicting thoughts

Hey guys, I'd really appreciate your help and opinions. I [26/m] have been dating my boyfriend [24/m] for 4 years (we've just started our 5th) and we've been living together for 3 years. In January, we had a very emotional conversation on our feeling about the relationship. We both love eachother, but lately I can help but feel that I'm falling out of love and would be happier either alone or with someone more compatible. To make this easier to read, I'll list my concerns below.

1. We don't have many interests in common anymore and those that we do share, we no longer build upon and grow.

2. Sex. He's a vanilla top and I'm into a lot of different kinks and fetishes. He makes somewhat of an effort, but any of you who have particular bedroom interests know that it's just not the same with someone who tries to go through the motions to make you happy. Furthermore, I'm vers and enjoy sharing the pleasure and different roles and he refuses to bottom. For the last year, we've avoided penetrative sex and I'm mostly to blame for this. I'm average height (5'8") and I have a very petite frame, while my boyfriend is very well endowed. This makes bottoming very painful when he goes more than halfway in.

3. Kids. We've talked about this many times in the past and he really wants a couple of kids, while I've been on the fence about the idea. I'm still young and this is not something I can totally commit to. I've given this a lot of thought everyday for the past several months and I've decided that I do not want kids. For selfish reasons, I really enjoy my free time and the quiet solitude that home provides. I also do not want to raise children in an environment where one or both parents work all of the time. I'm very career oriented and the nature of my career allows me wonderfully rewarding side opportunities with good financial benefits. I acknowledge that it's selfish to not want to give this up, but having an average salary coupled with a mountain of student loans and wanting to own a nice house makes keeping well paying side jobs financially smart.

What I've been struggling with is that our relationship has been like a roller coaster lately. We have really good days (sometimes weeks), and really bad weeks. We bicker about little things more and more. I've been very frustrated because my BF is very needy and I'm very independent. I make a daily effort to show more affection and physical contact but no matter how much I give it never seems like enough. He really loves me and I'm afraid that I will never find this type of love again. We were a really good match when we first started dating but it seems like as we've grown, our needs and goals have gone down different paths.

Am I selfish for wanting to end a 4 year relationship based off of an unfulfilling sex life? Kids are a terminating factor, but I don't want to prevent him from ultimately finding someone that will make him happier. Right now I just feel like a really crappy person.