Search Results: bra size

I'm asking pretty much 3 questions at the same time but I really am lost.

I've ordered 3 sports bras from ASOS. I plan on returning the third one because it's too small even though they're all size S (36-38).

The other 2 look like they fit me (no obnoxious spillage anywhere), but the bras do feel tight. So I wonder, should I size up if these bras fit me but at the same time feel tighter? How should a proper working sports bra fit? I have bigger boobs so they're squished to my chest but as I said, they don't really spill out.

It's really a pain to get them off though.

I worry that size M (40-42) will be too big for me, 42 is definitely too big. I'm like 38-40 in chest size.

Does a sports bra loosen up or not? Is a slightly looser bra better than a tighter one?

I do plan on losing weight anyway...

I barely have worn a bra in my life, i think i do it once or two a month when i want it to make some outfits look better. My breasts are like medium size and very firm. I’ve always thought that not wearing a bra was the thing that kept them like that and i was supporting this idea according to a random article i read when i was 14, but now when i look into google it says different things. Like before i read something saying that not wearing a bra make them support themselves naturally, but now when i looked i saw things like they can sag because of gravity when not wearing a bra, which seems more logical for me, i guess?
Anyway, I know it’s a difficult question but let me know if you know anything about this subject please.
Me starting from tomorrow I’ll start to wear a bra just in case lol