Ay nako, I'd really suggest checking with your doctor or sa family planning clinic ASAP, kahit onti lang ang delay, better safe na may proper guidance kayo sa pagswitch from injections to pills, lalo na may spotting pa. A few of my mum friends nag-switch din before, pero lagi silang sinabihan ng doctor kung exactly kailan mag-start ng pills para walang gaps sa protection, kaya please don't just start on your own na. Good luck, mama, seryoso lang talaga ito one na dapat professional ang advice!