Yeah I have this too I'm about the same age as you, turned out I had an ovarian cyst that had ruptured and my breast were fibrocystic it causes me to have sharp pain in breast and even under my ribs and with movement and even when I lay down. Sounds same for you! My xray on my breast showed nothing either, they said its fibrocystic. I just take Ortho Tri Cyclen for my hormones about all you can do for it and I wear less bras more sports bras if anything, and use a heating pad. You can look up fibrocystic breast get on birth control sounds your hormones could be out of wack. If your already on BC might be time for a hormone test to see how your hormones are doing and change your BC to another one.
By the way I had no lumps in my breast as of now or yet with fibrocystic breast changes, you can still have it without lumps showing there face. i know how lovely lumps

! Its usual bad around my period but I can feel it other times too well almost all the time ..more like it...it causes me to even have a hard time laying on my side back or anything.
I started with fibrocystic breast just hurting under my right breast too sharp stabbing later it started to burn, then it was in the left breast too.. about few mths later i had a cyst on my ovary and then a rupture. Now I get a cyst here and there that ruptures and I deal with the breast bologna. So just hormones out of wack really just one of those woman things that spiral out of control birth control is about the only option they had, cause I def not ready for a ovary removal. It took 3 docs to finally figure out I had fibrocystic breast so wasnt easy to figure out... i suggest to watch for ovary cyst, fibroids, endometriosis, etc.. and female issues if u do have fibrocystic breast changes cause that def means changes in your female system unfortante. There was no real test to see for the fibrocystic I had a mammogram basically but it showed no lumps but they concluded this was the start to fibrocystic breast changes and disease (so this is early signs in other words) next few mths came and I was in the ER with a ovary cyst rupture. Ugh... This hasnt been fun at only 25 yrs of age totally in shape and healthy lady till this looks like something I'm gonna have to live with.. I later found out that fibrocystic breast problems and disease are usual seen in women getting closer to 30 or in 30s

try taking magnesium, Taking 400 mg a day may reduce breast pain.
If you get any new advice on whats going on pls let me know.. best of luck!