That suggests it is breast tissue, not an infection -- and therefore is responding to natural hormone cycles. Still, I suggest you bring it to your ObG doctor's attention next time you have a routine visit.
Thank you,
Other thing I forgot to mention is that this thing, whatever it is, or condition in my nipple, accentuates every time my menstrual period is about to happen.
Does this mean it is related to hormones?
Do this offer any other clue?
Welcome to the forum.
There is no STD that mimics eczema; it doesn't happen. Equally important, no dermatologist would ever be likely to misdiagnose eczema. It is an exceedingly common disorder, easily (and accurately) diagnosed.
Given your partner's infideility, you should be tested for common STDs -- chlamydia, gonorrhea -- and rare ones for which accurate tests are available, i.e. syphilis and HIV. Even if one of these were to be positive, it would have nothing to do with your eczema.
Finally, no STD could cause a breast "protuberance". However, that symptom should be checked professionally to be sure it's nothing serious.
Best wishes-- HHH, MD