My experience was really unusual.
We MC'd on 11/13/2010. We were 11.5 weeks or so along, and it was a horrible experience. We were told to stop trying for a few months, to let my cycle get back in check. We figured that first few weeks after the MC that we could have sex safely without getting pregnant (HA!). We also were pretty upset and well, sex was a big part of us connecting and healing. It was a very sad but bittersweet time, it brought us so much closer. I fell in love with DH all over again during those couple of weeks following the MC. It was so sad and he was so amazing.
Anyway, come december, I didn't get my period. I figured it was just the MC and hormones having to work out of my system and didn't really think anything of it. I was pretty sure it couldn't happen again right away, if ever. I felt normal, if a little hormonal. Occasionally I felt a little sick, but chalked it up to flu, normal winter illnesses.
January rolls around and something was happening to me psychologically. I was starting to get very depressed and agitated at the same time, which is a big red light for me that my bipolar is getting bad. I was still on lower doses of my meds from the previous pregnancy and not very motivated to see a shrink. When I finally ran out of my scripts, I still neglected my mental care...losing the baby, my dad dying, having lost both my grand parents the previous year, i figure it was all taking effect on me, and frankly I just wanted to feel awful. I blamed myself for the MC and I wasn't getting ok.
Around the 5th of Jan, my mood was starting to seriously affect my marriage. I wasn't just depressed, I was aggressively angry, and DH was catching the brunt of it. I hadn't slept in quite a few days and was getting horrible headaches that would cause me to vomit. I was starting to worry something was really wrong. I finally booked an appointment to get my meds addressed. The GP decided to pull out the big guns...Valproate...to help control my bipolar symptoms. Two days into taking it, it occurred to me that I hadn't yet had a period, and my boobs were swollen and painful. I stopped off and bought a pregnancy test, because I knew valproate is possibly the worst thing to be on when pregnant. I was worried, but still pretty convinced I wasn't pregnant. It was one of those "just take a pregnancy test....once it comes up negative, your period will start the nest day" kind of moments.
I came home and peed on the stick and tossed it on the table and forgot about it. DH and I were talking online and arguing when i noticed it sitting there and looked....in mid evil sentance, I stopped and sent him "Whoa...I'm Pregnant". He said "WHAT?!?! I knew it! I KNEW IT!"
It didn't sink in for me for about 3 days and 5 tests. But here we are. According to CRL, I got pregnant 5 days...FIVE DAYS after EDIT: miscarrying, finishing the miscarriage/D&C.
So, I didn't think I was, but I felt I should test. It was more a "get your period already" test. It just happened to be a positive one. =)