Hips growing - womanly issues

Okay, so -- I don't know if this even belongs in this section. I'm pretty flakey so far with using this site despite keeping healthy habits outside of it. I think its because I honestly can't figure out if my body just changed naturally or if I really did just gain unhealthy weight.

First of all, my BMI before and now are normal. It was pretty much at the end of being 20 and approaching 21, the scale went up maybe 5 numbers and my boobs got bigger. Basically, the band of my bra physically hurt to wear. Then at turning 21, my hips were in pain and pants/leggings/shorts I would wear before weren't fitting. I went from not having a butt, to having a butt now - lol. Within this time, I still got periods even though I thought maybe I was prego every month because nothing made sense.

So I have issues with thyroid and PCOS -- I went to my endo/gyno and they did all bloodwork and weighted me, they said that sometimes a womans body can just change with age. The results of everything, which I made sure to get checked too again with another round of tests, was that I was normal and healthy. But to me, its just bizzarre. I would have expected these things to happen later in my 20s, not early in them. I'm always being active and I eat bad foods just as much as good foods -- I thought that was just what being young was about, I thought my metabolism was going to be good for another couple of years too. So I don't know.

Does this sound like my body just went through a weird, natural-womanly change or that it is just mostly weight gain, not like bone structure change? Did any of this happen to you? I also want to add that from the time I was 12-17, I was mostly overweight because of thyroid issue and PCOS being unresolved and undiagnosed, but everything got taken care of after that -- thats also when I started to become way more active too for my healths sake and have kept it up with mindful eating but realistic eating too. So basically, what I was used to with my body from then on was the losing of weight and being at a smaller weight.

Sorry its so long. Thanks ahead of time for reading and possibly responding.