Bleeding After Sex

i got an IUD placed about two years ago, and about 1 month and a half after it was placed i stopped having a period. Back in april this year i started having a period again. within the past few month though i realized it will come for ab 2-3 days really light. stop for 2 days then i’ll start spotting again for a day or two. the other day i had my cycle for 3days and it stopped no sign of it for 3 days. i had sex with my partner, and after i got up i saw like water down bloody line on the sheet. Is this normal for other women with IUDs or could it just be from sex?