Okay okay so i'm AFAB but I can confirm, yes, breasts love to randomly hurt.
Welcome to womanhood.
I believe it's caused by estrogen levels. In women who are menstruating you get cyclical breast pain as part of PMS which is caused by the surge of estrogen that happens around the point of ovulation.
When your body is adjusting to the new hormones you are basically going through puberty mk 2, and yeah, the tissue growth coupled with estrogen just being like that can cause tenderness.
If it gets too awful a warm compress can sometimes help but ultimately i've found over the years you just have to put up with it.
It SHOULD settle down with you ladies though, because your hormone levels should be fairly stable once all the puberty changes have finished.
I STILL get the dang pain because my body is dumb and overproduces estrogen so I feel ya on it. I got a week of reprieve this cycle before they started to hurt again. *sigh* sometimes I also get the shooting sharp pain in the nipples too. I don't know what that is, just that it happens. It's like glass in the nipple or something, owww. No hugging, no touching, no sleeping on my front. Eugh. I guess it's easier to handle when you WANT the boobs though hahah.
If I remember puberty mk1 with breast growth, nipples also can get super sensitive and chaff far far easier so be aware of that. A little camisole will help if you're not at a point you feel you can wear a bra. Something soft anyway, so they aren't rubbing against anything coarser. Chaffed nipples are... really painful. I don't recommend it.
When they are REALLY sore, sometimes sleeping in a maternity or sports bra is actually the best thing I can do. Keeping them constrained stops em wobbling about and thus reduces the pain. I mean even small ones wobblea little when you move and if they're excessively tender, sleep in a soft t-shirt bra. t-shirt and post surgery bras are the best omg. Sooo comfortable.
But yeah, it's a common female complaint. Estrogen is a wild ride heh. Congrats ladies on the desired changes! How exciting. It never ceases to amaze me how effective hrt IS. It's like magic!