What Causes Missed Periods With Spotting During Periods?

i recently came of the pill ( i was on it for 3 years on micrgram an then loistern 30) i came of it 9 days ago and had unprotected sex that day the day before i used to forget to take it sonetimes aswell an the next two days... i had a period but it wernt like my others it was much lighter an alot painful i have had nearly every sign of bein pregnant apart from missed period could i be pregnant and is it to early to take a home pregnancy test.. am trying for baby.