Period cramps after heavy exercising

I exercise regularly the last 5 years but the last 6 months i start exercising harder and do a lot of heavy cardio workout and i started getting very painful period cramps a week after my period every month after my cardio workout and usually i keep spotting for 3-5 days after it

And its not only cramps i also feel nausea and it last for an hour or less than i feel okay and start spotting