help. my period is doing crazy shit

Tiffany
So I'm on the pill and I've always been really good about remembering to take it. My period always follows the pill pack pretty closely and I've never had any issues in the past. However, my period has been doing stupid shit the past few weeks. I got off of my last full on period about 2 1/2 weeks ago like planned. I was like sweet and started wearing my cute Lacey VS panties again. Then my period strikes again a little over a week ago (so only a week and a half between my periods, and this was fairly heavy). It seemed like it officially stopped a few days ago and then of course, I start spotting again yesterday. 
WTF IS GOING ON! I'd like to wear cute panties again and have sex but at this rate, i don't think I'll ever be sure enough to wear my VS. 
Anyone have any idea what could be going on?