You sound like me!
I had a MMC at 11 w 6 d in June, and I had a 45 day cycle, 42 day cycle, 37 day cycle before I got pregnant on a what would have been 32 day cycle. I was always 28 day cycle before then.
It was very very frusturating. I believe what helped me finally conceive, besides prayer, were OPKs and Instead Cups. I had no idea what was going on with my body, so I bought Answer OPKs (cheap OPKs you dip in urine) and used them every day from day 10. I also bought CB happy face digis, and used them when I was unsure (as the lines can be confusing, though once I got a + with the Answer ones, I could definitely tell.
I got a + on day 17, so I O'd somewhere between day 17 and day 19, but I never would have guessed, since my cycles varied, and were closer to 40 days since the MC.
My advice is to use a fertility monitor or OPKs or temp so you know what is going on. I swear by Instead Cups now (which you will see some positive threads on if you search. They're $7 for 14, and are typically used for your period. But, they go up in your cervix so you don't lose any swimmers!)
Good luck and

!!