(NSFW) What could be the reason I haven't yet started menstruating?

I started taking the birth control pill Microgynon three weeks ago, I’m currently done with it and I’m on my one week break so that I can have my periods, It’s my first time ever taking the pill so I guess it can have it’s side effects but I’m very worried because three days have passed and I haven’t yet started my periods.

Before I begun on the pill my period always begun somewhere in the beginning of each month. Yesterday my boyfriend and I had sex and afterwards after I went to the bathroom I happened to notice some blood and that left me thinking that maybe my period was about to start, but I was wrong because obviously It’s not here yet and I’m very worried.

Is this normal, has it ever happened to any of you? My doctor when he was prescribing the pill to me he told me all about it and how my period should start immediately the moment that I stop taking the pill.

I’m starting to think that I’m pregnant, I even bought a pregnancy test 2 weeks ago because recently I’ve become more hungry lol. I have yet to take it but I was waiting for my last week of pills to finish so that I would see if my periods would start or not, now they haven’t and I’m left in shock.

My boyfriend tells me it’s impossible for me to be pregnant and he tells me it’s maybe stress. Also keep in mind he’s never really cum in me, only maybe a few drops.