What are the chances I might be pregnant?

Long story short - My little girl was 7 weeks on Saturday, and I have been having a few symptoms the past few days that I only experienced during early pregnancy. I am breastfeeding and have not yet had my first period, but my husband and I resumed relations around 4 weeks.

I see a lot of anecdotal evidence about how a woman is actually "most fertile" in this 6 week window after she gives birth, but no reliable sources or definite details. Anyone who could direct me to Web sites with this information would be greatly appreciated!

The details on the situation are as follows: The first time my husband and I had sex after the birth, we were both too into the moment to stop for a condom. It was 4 weeks following my delivery. We have used condoms each time since then. About 1 week ago I started noticing that I was feeling slightly queasy when I was brushing my teeth in the mornings. This is the ONLY early pregnancy symptom I had with my little one, and I can't recall ever having a period of time where I consistently got queasy while brushing my teeth other than in early pregnancy. I will be getting two tests today so that I can take one when I get home and a second first thing in the morning, since I haven't had a period and don't know when I would be "late." With my little girl, the queasiness started just a couple of days before my missed period, so now that it has been going on about a week, I expect that possibly enough time has passed - also, it's been just over 3 weeks since the only time my husband and I had unprotected sex. Also, I have had unusual discharge, but that may simply be hormonal changes.