Hi Dr, I'v Been Using Triphasil 28 Since Last Yr

Hi Dr, i'v been using triphasil 28 since last yr the dermatology prescribe me a tetralysal 300g and he said it wont make the pill less effective bt im worried since its an antibiotic, i had sex on friday then saturday i bought a morning after pill bt today morning i was supposed to get my period bt i didnt, i stop drinkink tetralysal on thursday, can i be pregnent