11 months PP, workout causing bleeding/period?


I was very active in fitness before and all through pregnancy. Started back yesterday with basic 30 min workout video. Today, I ran a mile and did about 5 min of ab work. Later this afternoon, I realized I was bleeding. Period isn’t for another 6 days. (I have an iud. Got my period back at 6 months pp) Is this normal? Put a panty liner on this evening and it was bright red blood. Would it be my period early from all the activity or something else? Even though I haven’t worked out in 11 months, I stay active daily. (Teacher) Any thoughts are appreciated.