Can Someone Answer This? Help

My husband and I have been ttc for about 2 months now. The first month I came off the pill I had a 32 day cycle and a normal period. This past month we got down to business to try for a baby. About 2 weeks ago I started getting nausea on and off, not bad enough to vomit, just a lot of acid in my stomach. Lately I have also been experiencing lower dull back pain and dizziness. I am 3 days late for my period now and am on day 36 of my cycle. I did a pregnancy test and it came back negative.

Is it possible that the pill is causing me to have a longer cycle even though my first cycle off the pill was pretty good? Could I be pregnant even though the pregnancy test is saying negative?

I'm really confused, help!!