Can I still be pregnant?

Okay so i need some reassurance. In May I started taking Spironolactone for my acne. One of its side effects its irregular periods. The first month [June] on it I got my period on schedule, next month [July] it was a week late. About two weeks after that period I had spotting here and there, sometimes I thought it was my period because of the flow but after a few hours it was nothing, that lasted about 2 weeks. I was suppose to get my period last week of August, 5 days later I still did not get it so I decided to go to my OB, I explained, I took a pregnancy test and it was negative, I was put on bc [Enskyce]. I started those the following day, today marks 11 days of my period being late and will be day 6 of my first pack of birth control pills. I have never taken the pills before, but since I started them can that also play part of my period being late or should I get tested again? TIA