Bulge between breast and armpit

Its breast tissue in the armpit region, it usually doesn’t go away without a bra on and you can get breast cancer in that area (if you have breast tissue), so to anyone who has this make sure you do your self checks there too (not just on your breasts). Also, it’s decently common if you look for it on other people.

Accessory tail of Spence most likely. Technically you can get extra breast tissue anywhere along the so called milk line that extends from the axilla to the groin. It’s in a similar fashion to supernumerary nipples in humans that occur in the same line.

I call it Sleevage

Not a medical professional, but always assumed that was just fat and where the pectoral muscle connects to the shoulder joint. 

Also, side note. Your curls are on point.

Could it be the bra being too tight forcing or holding everything up?

I think the breasts are pushing up due to the tight strapless bra. Do they go away without the bra,

probably caused by the bra. it can also be lymph related. There are major lymph nodes in the armpit called the Axillary nodes. This person may have some minor lymphdema (pooling of lymph) caused by the bra or other health issues.

I have this. I’m skinny too. It’s so frustrating.