I've been spotting for 3 days and stopped now it's heavier why ? i had sex but he didn't finish inside it happen 10 days before my period

Irregular: It's not totally abnormal for a woman to have an irregular cycle in which there is some spotting outside the full period like you experienced. Sometimes our hormones just get out of whack a bit and we end up with some intra-cycle bleeding and spotting and it's not abnormal and you don't need to worry too much even though it's a pain for you. Having sex didn't affect this at all. No worries.