heavy to light periods???

so like i usually have pretty heavy periods and stuff and it’s normal for them to be pretty bad but my last period was AWFUL it was so heavy and i always had to change whatever thick pad or super tampon i had every 30 minutes. there were also so much clots too. so i haven’t really exercised over the past few months cuz i’ve been busy and my sport seasons were over so i got pretty lazy but i also just had a pregnancy scare so idk. but now my period that started on wednesday which was a few days after i just started to workout and exercise started off as brown and i was scared because that has never happened and now it’s super light. not light like spotting it’s still a lot of blood but never as much as it usually is. idk if it’s because i’ve been exercising, because my last one was super heavy, or becayse i have a chance of being pregnant. i just need some advice pleaseee