Would I be getting a positive pregnancy test by now if the last time we tried was 12 days ago?

My cycles have been jacked up for the past 5-6 mths. I've had like two periods. One cycle was 42 days and the next was 44. My period app says on average I should have started on Monday. Well no period so far. I have felt somewhat crampy, but nothing. The last time we tried was 12 days ago. I was just wondering if it's too soon to get a positive on a test according to the last time we tried. I took a frer today and it was negative. I went to doc and she thinks I'm not ovulating since my cycles are so long. She gave me a script for provera but I'm scared to take it just in case I'm pregnant. Any thoughts?