My Periods Are Very Consistant, Even After I Became Sexually

My periods are very consistant, even after I became sexually active. Last Sunday 10/11 I started birthcontrol and had an allergic reaction the following Saturday and immdetaly stopped taking it. Tuesday 10/20 I noticed I was spotting with slight cramps. Ive never expirenced spotting between periods. I was having intercourse approxiamently three times a day between the 12 and the 16 and pulled out half the time and used condoms the other half. Is there any way this is implantation?