I don't have any advice, but I hear you. I (27F) have two girls (X-22mos & B-4mos), and we're done. I have PCOS but I didn't know it until we tried to get pregnant and failed. Once we figured it out, we got our first baby girl. I grew up in a family of boys. I have a much older sister who has two boys, a brother with 4 boys and a girl, another brother with a boy and a girl, and 3 more brothers, with no kids. I barely knew what to do with a girl, as my one niece came along when I was in college, and my other one had some behavioral issues so I didn't get to see her much. Everything was always boys. I was a Tomboy; I played hockey for 8 years, and generally preferred guy friends (they just felt like less drama).
So, when I found out I was pregnant with a girl the first time, I literally panicked. When it was a girl the second time, I felt a pang of sadness knowing that I wouldn't have one of each, but we'd decided on two, for reasons we both agree on. It's harder when people say, "but you're so young!" Because I think, Ok lady, don't try to live vicariously through my uterus, you don't know why I only want two kids, you didn't even ask.
Our reasons are: 1) the numbers - we each have 2 arms, and there are two of us (and we're definitely not looking to expand that part of our family). Quite simply, we don't want to be outnumbered.
2) we both came from larger families (mine 7 with big age gaps, his 4 with small age gaps) and both felt like our parents failed us all. The worst part is, our siblings feel the same. We all agree, they just dropped the balls. Not one ball. All of them.
So, one is very logical, and one is very personal. Ultimately though, we're on the same page. My heart aches a little when I think of the little boy who could move in nicely to the already blue room (shhh) upstairs. It just feels like it wouldn't be fair to any of them if I get selfish and then, well, drop the ball(s). But that's entirely our own thing. Do I think all people who have more than 2 kids are somehow failing them? No, not at all. This is just about what we feel like we can handle well.