Why do you think you need to wait till the 17th April? Working on the standard 28 day cycle (and remembering that lots of us don't have those!) I would think you could expect AF any time from today, as it's 4 weeks from your LMP, even though you say your cycles are irregular (I presume you mean they were before you were on bcp?). I would test again in a couple of days, try to get a test that has the 2 lines like Confirm or the standard Crystal Clear, and don't forget to use first morning urine.

The BCP could well have mucked up your hormones - especially as you skipped the last "period" - my first cycle coming off BCP was 56 days! and it took 6 cycles before I got pg, despite charting all that time, with cycles that were 44 days, 32, basically all over the place. And I have 28-29 day cycles naturally. So dont' despair if you are not pg, if you want to be, although you might take heart when I tell you that a good friend got pg first cycle off bcp.