Could just be freak constitutional short genes sneaking in. Could have had, or even still have, growth hormone deficiency, hypothyroidism, a skeletal dysplasia, especially given the described discrepancy between trunk and limb proportions.
Given that bit I’d wonder about hypochondroplasia or SHOX deficiency?
I’m not one to rush to discuss with a real life doctor for everything but it probably is worth it. Even if just to know.
Well, no matter how you slice it, they’re her pants.
Hehe, I was diagnosed with hypothyroidism sometime in my 30s. I could fall asleep anywhere at a moment’s notice since I was a teen. I went to the doc because my foot was swollen for weeks, and I had no pain and didn’t know why it was swollen. He figured it was gout, but ordered blood tests to confirm it. I went home and looked up gout. Gout’s calling card is intense joint pain, which I told him I didn’t have. So I did some more searching, and figured I might have hypothyroidism. Blood tests came back, and yeah, hypothyroidism.
It doesn’t make any difference in how tall I am now, but treating it at least made it to where I could do something other than nap after being horizontal and still for fifteen minutes. To this day I watch TV while standing up, because I’m still pretty nappy if I sit down and relax while watching it.
I hit puberty at about 10-11, I don’t know if that’s kind of early.
I had a growth spurt but only 1 and only 2 inches and at 14-15.
How old are you now?
I’m an adult now.
That’s not my question. Are you in your 20s, or older?
Older.
What are you hoping for from this thread?
You are correct that statistically your being the height you are with the family genetics you have is unusual. That does reasonably raise the possibility that there is some pathological etiology, some cause beyond normal constitutional short stature, and knowing if there is may or may not be of value even though that knowledge is not going to change your current height. The cause is not likely to have been your difficult and premature birth. Not as a major factor anyway.
None of us can tell you if there is or is not a pathological cause, or anything else in particular to be evaluated for if there is. That last part is probably the reason to get it investigated more by an expert who can evaluate you in person some skeletal dysplasias for example also increase the risk of spinal stenosis …
Is it just genetics?
I mean, the odds of me being 5’2 with all the heights I listed can’t be very high.
Quite possibly. As already discussed, several of us are shorter than our parents.
But likely not zero, or even close to it.
We’ve gone around the tree with you several times in this conversation:
Beyond that, a bunch of laypeople on a message board who don’t know you aren’t able to give you much more information than you’ve already gotten (which, frankly, is quite a lot). If you are really concerned that there might be some other underlying health condition, then, as several people have suggested, see your doctor.
The prediction for the average male born of your parents is 5’9”. You are significantly more than 2.5 SD outside that prediction. Which happens by chance a nonzero amount of time. Actually @kenobi_65 for these purposes relatively close to zero. I would more surprised by no pathological cause than by there being one.
Again what are hoping to get as an answer from this thread more than that?
If you do end up seeing a specialist please do let us know what happens.
Fair enough; I am a statistician, but not a medical guy, so I defer to your knowledge here.
Well this is the intersection! 
2 SD threshold is said to be 3.9” (10cm) around the mid parental height prediction. He’s 5’2.25” and the mean parental height prediction is 5’9”. Two SD outside is 5’5” …
FWIW I take that taught number with a grain of salt, adding more if parents are at very different percentages. But here not.
Using those SDs what fraction is expected to be his height?
For an answer. I’ve heard it’s just genetics, but I feel like it’s unlikely I’d be this height with all the heights I listed.
Perhaps the odds that the son of a 5’ 5" man and a 5’ 8" woman is 5’ 2" is small, but it’s not one in a million or such. Perhaps it’s more like one in 2,000. 1 in 2,000 is not that rare. Everybody had some set of physical characteristics about themselves that combined happens less than once in 2,000 times. Again, go to a doctor and talk about this. We can’t be any accurate help to you.
5’5 man and a 5’8 woman
Other way around.
5’5" man and an 8’5" woman??
1 in 2000 is one kid in my high school. And one in the next high school. And the next. And the next. And then again 4 years later w a new crop of kids.
Is our OP the unlucky short straw drawer of his high school cohort? Certainly quite possible. For damned sure somebody had to be.
Once again, I’m not checking my posts carefully enough. I didn’t mean that. I meant 5’ 5" woman and 5’ 8" man.
Oh probably not even that rare. I’ll defer to the statistician on that! Still coupled with the self described shortish limbs and stocky build … enough of a chance for some skeletal dysplasia to investigate I’d think.