Ice & Roller Hockey Goalie Masks and Helmets

At Hot Topic, my shirt size is S.
At Tilly's, my shirt size is M
And my Juniors Arizona Jean size is 3.
I love to shop at a clothing store called Express and I'm a size XS in their dresses. But their clothing is for adults and I haven't even started high school yet.

I'm a real jock, people always tell me it's muscle and not fat. Most of my friends are boys so I don't usually talk to them about my concerns. And my boyfriend is really pissed that I didn't defend myself when another girl called me chubby.

[I already asked a similar question and most people told me I'm healthy, but just in case, I thought I'd ask again because my brother says im really overweight.]

PS-please do not warn me about anorexia or having a low body image, just serious answers, please