10 day, light period - not typical

So I have endometriosis but fairly regular periods. I pretty much know by keeping track when it will start and stop and they are typically debilitating, heavy, horrible periods with lots of pain that lasts 4-5 days. But this one has been different. This one has been light with almost no pain, but lots of lower back pressure/aching and extremely sensitive and sore nipples (for 2 weeks now) and the flow has lasted for 10 straight days (spotting/light flow).

My husband and I were trying to have a 2nd child for 6 years but we haven't been actively trying for a few years now and have accepted that we won't have another child.

Opinions please..... is this just stress induced/fluctuations in hormones? Or is could this be early pregnancy? Or could these symptoms: 10 day "light/spotty period" with tender nipples and lower back ache mean something else entirely.