cp3, here's a few reasons for bleeding in early pg: (from babycentre)
In the very early stages of pregnancy, as the fertilised egg implants there can be a day or two of light bleeding. Later, as the placenta embeds in the uterine lining, it causes slight bleeding. Sometimes a woman will experience 'breakthrough' bleeding.
Pregnancy hormones cover up a woman's usual hormonal cycle, but variations in those normal cycles still go on. Some women notice bleeding at around the time they would usually have had a period as a result of this 'background' variation in hormonal levels. And occasionally women will experience a cervical erosion (a softening of the cervix), which can cause bleeding in early pregnancy.
Bleeding can also be associated with a vaginal or cervical infection or a polyp (a benign growth) and can also occur after intercourse. Sometimes it's not possible to decide what has actually caused minor bleeding.
It's worth talking to your midwife or doctor about any bleeding in pregnancy. Often light spotting is not considered a major problem. But spotting or fresh bleeding, especially if it's accompanied by abdominal pain or cramping, needs immediate attention, as it may be the sign of a miscarriage, an ectopic pregnancy (where the embryo implants in the Fallopian tube rather than the womb) or, in later pregnancy, a problem with the placenta.
Having had some bleeding in early pregnancy, it's natural to feel concerned. Call your midwife or your GP.