help Spotting

So im on the pill ( zovia) i have taken them regularly i only Missed on the 30  of dec i doubled the Next day And on the 2 i took it late And i drank so i might have vomitted it  
Yesterday i took it and had sex after 6 months w my bf so today i am having cramps And im spoting ( really light blood) only when i wipe 
Does anyone know why am i spoting ???