Boob pain

Yesterday out of no where I got a painful feeling in my boob, not the nipple or around it but like the bottom fatty part

It’s so painful and only one side

I am currently BF a 18 month old and only on the side ( don’t ask lol, the other one barely had milk)

I’ve been ttc and i duno if it could be a sign of pregnancy? Tested positive on my opk but negative on a pregnancy test (af not due till June 28) but couldn’t help it

Can someone help!?!😫