because of the friction created between the t-shirt and the nipples....
Maybe the friction caused by your shirt. I can think of no other reason.
Breasts do not HAVE to hurt to ovulate. However, it is often the case that they do. It depends on the person. Some times a womans breasts hurt, while another womans dont.
Depending On how big both your breasts are if there both about the same size as you hug they can bump each other which can hurt them,the preasure of breasts pushing hard into breasts can hurt them too,try not to let your breasts bump her breasts as you come together for the hug,also when together dont squeeze each other tight as breasts can crush breasts doing that,if your friends breasts are firmer than your breasts that can also be a problem,firm breasts against soft breasts can hurt too. Hope this helps you out .
natural growth, no it doesn't hurt
Are they growing?
Yes! Very bad!
No.
No. Your boobs come as a surprise, but it doesn't hurt when they grow
if you have entered puberty, your breasts will usually be sore from time to time
Yes. As breasts grow, it is normal for them to be tender or a bit sore.
See a doctor
Developing
Your period may beggining or they are growing