Hello,
Welcome to the ehealthforum and I am glad to help you out.
I can understand your concern as bleeding and spotting are unlikely in pregnancy. But spotting may occur in pregnancy due to corpus luteum defect of pregnancy. The corpus luteum secretes the hormones for sustaining pregnancy till 12 weeks after which placenta takes over). In corpus luteum defects, there is increased brownish spotting and if this is the cause then you may need progesterone supplements till 12 weeks of pregnancy. It can also be due to an impending miscarriage if there is an associated abdominal pain or cramps and the spotting turns to frank bleeding.
I suggest you to consult a gynecologist and get a through physical examination done. You also need to have complete bed rest. Avoid lifting heavy weights and climbing stairs.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care.