Stopped the pill. Late/No period

Hi, so I started the pill last month on the first day of my period 15th July and was on it for about two weeks but was bleeding the whole time and had bad headaches so stopped taking it. My last period was then due obviously around the 15th of August as I'm usually regular (before taking the pill). I haven't come on since 15th is this normal for when you've stopped taking the pill? Ive done a test and it was negative so I'm almost 100% sure it's not pregnancy that's stopping my period.

Any ideas or similar experiences? Thanks 🙂