Pill 💊

Okay lady’s would love some help I just started the pill after being on the shot for a years and a half. Well the dr told me not to worry if I don’t start my period until after the third pack of pills so I was like okay cool. Well I didn’t start my period but when I started the new pack me and my fiancé was having sex and I started to bleed after well then I bled for a day filled half a tampon and then stopped so a few days later the same thing happens after sex any ideas what is goin on??