No Period?

I just started yasmin this month. I started my period on a saturday morning so I took the pills then, opting for a direct start rather than a sunday start...It was pretty close anyway. I take my pills in the morning when I wake up, between 9:00 and 11:00 each day. I've never missed a pill, though one day I forgot to take it for a few more hours, not until that evening...Less than half a day late. The instructions say that if you miss one pill, you don't need backup contraception.

Anyway, I had sex for the first time on my third week of the pill. We used condoms of course and they didn't break or leak as far as I can tell. I wasn't late with a single pill that week and the one pill that I was half a day late with was a whole week before that, if not more (can't remember the exact day). There shouldn't be any issues.

Now i'm on my first week of placebos ever. It's the end of my 4th sugar pill day and I still haven't had my period. Most people I know don't start until the middle of the week and that was today for me. I still haven't had my period. My normal cycle is very off...I have my period every 2 - 2 1/2 months, when i'm not on birth control. Since this is my first month on, it's only been three weeks since my last period. I read that sometimes on yasmin people will miss their first period, when they first start out.

Should I be worried or is it normal for this to happen, given my completely abnormal cycle. I can't think of any reason i'd be pregnant...No breaking, no missed pills. Do you think it will come by the end of the week and, if not, that i'm just one of those people who miss their first period?