Questions???

Cydney
Can one get pregnant if they take their birth control pill AFTER having sex? 
And occasionally missing a pill and not double up on them ? 
Also how long does "spotting " occur when one has missed a pill ? And should there be clots in it as it is when we get our periods ?
It's been a little hard tracking my period since this happens to me and then I'd have this light spotting for a day or two then stop , but the. Come back out of no where and while taking the pill consistently... I'm ready to just stop taking them all together !!! Ugghhhh so frustrating