What Causes Random Bleeding?

hi i have been on the pill for 4years never had a period i ran out didnt take it for about a week and half got my pills from dr and took it for 2days then i forgot for a few days took it for 3days and then a week without the pills i had sex then i not long after i bleed for 3day like a period brown red then fading, then i had sex again and bleed for about 30mins then a few days later my partner fingered me and i started to bleed bright red i've been wit my partner for 5years and never had this problem could u give me any advice please thanks