Not sure what to tell you but I've been on the mini pill for almost 2 months now and my period's been a bit weird too, with lesser time between periods and today a couple of days after having sex, I've noticed some brown blood bits, just like the end of a period. I'm not too worried though as i read that it may take the body a while to get used to the pill.
This is quite normal lovely, the pill will be playing a part in this as well as you being PP, it takes quite a long time for your period to become regular again after birth although I know some girls who have had no issues with theirs and have been normal. Its been 3 and a half months for me and mines is a mess lol. Its lasts like 12 days now and just doesn’t come on time like before just when i think the end has come i start bleeding heavily the following day again haha. If you feel worried or your body doesn’t seem right then definitely speak to your GP but I wouldn’t worry too much x