Call your OG/GYN. You may have an underlying issue causing your cycle to be so far apart. As that I just talked to my OB/GYN 2 weeks ago about mine being irregular and I've been TTC for a year now, he said "Normal is within 8 days of 28 days." He explained that even if one month you're 20 days and the next you're 36, you're still medically within the "normal" range. (Mine range from 26-34 days!) As that we've been TTC for a year, he's having my hubby do a Sperm test (If he'll go! See my question to understand.) and then if we're still not pregnant by August, he'll start running the tests on me.
The fact that it was 40 days between means that you ARE NOT medically "normal". Chances are they'll want you to wait a few more months to let the BC work it's way out of your system, but considering you had a MC, they may want to take a closer look.
Here's wishing us both a "Blessed" year! May we both find ourselves "in the kitchen, barefoot, and pregnant!" ~J.