How long after starting birth control should my period start?

Sabrina • 22, Criminal Justice major, and with my boyfriend for almost 4 years. Our dog is our kid!
I'm on the second pill of the second week (9th day) in the birth control pack. My doctor said I should start on the 4th day? I haven't yet. My period is now 3 weeks late but two HPTs have been negative and an additional urine test at the doctors was negative. Thoughts? Advice?
Please no negativity, such as saying I should have been on birth control in the first place. I moved back home and my insurance was put on hold while the paperwork was being transferred from the other county I lived in, so I couldn't get BC for a while.