I can tell you from my current experience that it is possible to continue nursing before and during pregnancy. I am almost 6 months along with my second and still nursing my 18-month-old. The milk has dried up, but he still seems to need the comfort. He typically nurses to sleep a couple times a day (and night), for maybe 5-10 minutes. So if you are both still enjoying it, keep going!
About getting pregnant -- it is true that some women need to stop nursing completely to get pregnant or sustain a pregnancy. If you are having cycles (even if they are longer), there is a good chance that you are ovulating. However, you may not ovulate if it is just the first couple of cycles and just bleed. If you are ovulating, it may be that your hormones are not stable enough to support a pregnancy yet. There are easy ways to tell this, including checking mucus and taking your temperature first thing in the morning. There are various methods out there to help you figure out what your body is doing -- I like the Couple to Couple League information (www.ccli.org) about Natural Family Planning (NFP). They have classes and home study materials, as well as other resources (like thermometers and such). NFP is a very useful and effective method in both achieving and avoiding pregnancy.
Otherwise, La Leche League and kellymom.com have been good resources for me in learning about breastfeeding and weaning issues. Hope this helps!