Pregnant? I had the same symptom when I was mildly pregnant. It started in the breast I slept on, and even go away during the day, and then several days later it was both breasts and all the time.
If it’s impossible that you’re pregnant then you’re doctor might take xrays again (was your last mammogram a 3D mammogram?) plus a sonogram, or even an MRI.
Don’t ignore breast pain. Especially, if you have pain in one breast and not the other.
All my friends who had breast cancer before age 50 found their cancer either because they had discomfort or felt a lump, and it wasn’t found on mammogram, they needed additional tests to see the cancer. The 3D mammogram they do now should be more sensitive though, but still you know when something isn’t right, you have to push for more than a mammogram if your doctor doesn’t automatically order it. In my non medical lay person opinion.
Maybe doctors run a blood test for prolactin? I don’t know if they do that for breast pain or just discharge from nipples. That should be symptoms in both breasts, but like I said when I was preggers initially I felt discomfort in just one when I woke up in the morning from being on one side.
I’d call my doctor and see if they will order more tests without seeing me if I had just been there a month ago. If not, I’d go ahead and make an appointment with my doctor, so they can make their money, and then they will order the tests.
Does your breast look unusual? Redness or dimpled skin or something else?
I’m not a doctor. Everything above is not advice, just my own experience and what I would do.