I had unprotected sex on the 2nd of march, buut I took the morning after pill less than 24
Hours later. Had sex again on the fourth without a condom; but I started my birth control pills
That following morning. (the pills "aviane") Then we had sex again unprotected on the fifth. I took my pills every day since then, and I started the placebos today (26) but I still don't have my period.. Could I be pregnant?

Yes, as I am sure you know, the birth control pills that you first started were not effective when you had sex. It takes three or four weeks for them to take effect.

So there was no protection at all.

The only other factor is that of course the morning after pill which can effect your cycle.
I would wait another week and try a home pregnancy test.