Jennifer....to be honest I can't remember, but it wasnt as quick as you, but wasnt too long either. They say it returns as normal (when it would be due without Mirena).
POAS this morning and got another BFN (10DPO). Symptoms have all stopped, and it is unusual for me to not get a BFP by now, so I think i'm out this month :( I was much happier to conceive July or August, but now I'm disappointed, hehe...go figure!
ETA: I only have a 12 day luteal fase so I think that's why I normally get BFP's early.

