implantation bleeding or pregnant?

Delanie
so i can't tell if i'm having implantation bleeding or if it's just my pills.. 
a pill pack or two ago i skipped my placebo pills and went straight to a new pack ( i did this one time). and then when i continued with my next pack i let my period happen and it was successful. my boyfriend and i use the pullout method and he had never finished in me. a few days after we had sex i had a light bleeding and cramps for about 3 days. now i am 3-4 pills away from my period. i don't want to wait for a pregnancy test but also have no money for a pregnancy test.