Longer cycles after miscarriage?

My cycle came back June 30th after my miscarriage in late May and lasted a few days, but it was only some spotting. I actually didn't consider it a cycle until I called my doctor's office and they told me to count it. So I counted it and noticed that my cycle came back 31 days after my loss. Before my miscarriage, I had a pretty normal 28-30 day cycles, so I was pretty pleased that, despite the weird period, my body was seeming to return to normal. Now, here I am on cycle day 36 on my second cycle with no period and a handful of bfn tests. I'm going crazy! Has anyone else had longer cycles all of the sudden after a miscarriage? Could have ovulated late this cycle and be pregnant but just tested too early?