There are many reasons for spotting in an otherwise healthy pregnancy. Sex or even just checking can irrittate the cervix, which is very soft and engorged with blood right now. There can be a slight dip in progesterone around when you would have gotten your period, because the placenta hasn't switched on to making its own progesterone yet. Sometimes there is bleeding when the placenta starts to seperate from the yolk sac and embed itself into the lining. Sometimes you just spring a leak. I did a lot of research when I started spotting, and as many as 35-50% of women spot during pregnancy and only about 25% of those go on to miscarry. The best signs are if there is no cramping, no increase in flow over 24-48 hours, if it lasts less than three days, and of course, what your blood levels are like.
*hugs*
I know this is really hard and scary. Try to hang in there.
~Rose
Follow Mothering