Long cycles after coming off birth control.

Hey guys 
Just wondering if any of you are in the same boat or have been...
Came off pill and had withdrawal bleed 25th November. The next period I had was 34 days later and I'm now on my second cycle but am on day 38!! No sign of AF but getting BFNs. 
I've been having cramps on and off all week with slight nausea and tiredness but it may just be me overthinking it!
When would I likely show up a positive line if I am pregnant should it be by now if I was? 
Appreciate any responses/advice