Can exercise affect changes in your period?

So this past week I finally started going to the gym and I’ve gone roughly every other day for about an hour.

My last period ended a week ago and today after getting back from the gym I noticed I had some spotting. I never spot between periods so this kind of alarmed me a bit.

Should I be worried it may be something else or could it just be my body reacting to the abrupt change in physical exercise? (Maybe I need to take it down a notch haha)

Also just to frame context I am sexually active but with my girlfriend so there is absolutely zero chance it could be pregnancy. I’m not on birth control so that isn’t a factor, and we are both clean so it can’t be an sti.