Lutera birth control

Charlotte
I took Lutera birth control pills every day for 2 years until I ran out of them November 2013, and fell pregnant with my son 3 months later in February 2014. I recently just switched from Microgestin Fe 1.5/20 back to Lutera last week. Never had a period last month due to it being one of the side effects of the Microgestin Fe1.5/20. (I took 2 tests a few weeks back. Both negative.)
And now, I'm just trying to remember how long it takes for the Lutera BCP's to get back into my system.