I dont know if this is related to HRT but i have been feeling pain on my armpits for the last 2 week.  I firstly thought that it was a result from gym but i havent done any exercices involving the upper body since june..

My breast buds started to form around same time, could it be related ? i would like to be enlighted  it got me a little worried because i just got another peak after taking my estrogen dose, thank you.

It could from swollen lymph nodes, you may want to see your Doctor for a checkup.

Breast tissue extends into the armpits, that could be your boobs coming in. When that was happening to me my friend, a cis woman with ample boobage, suggested that it could mean big ones.

It's possible, but best be safe and still get it checked out to make sure it isn't anything else that does need dealing with. Hugs
Mariah

thanks for awnser, i will get this checked next week if it persist.

I could explain the pain as if a shock was sent from my nipples to armpit then to middle of my bicep.

I don't recall the details as it was a long time ago, but I got all sorts of odd feelings when I started. Before that I'd somehow thought that breasts were only in front, but they go way back under your arms. I didn't realize they hurt either. Its like some kind of women only secret.

It's likely breast growth soreness.