Spotting can happen a few times during pregnancy, stress can be one of the reasons, irritation of the cervix caused by sexual intercourse, the pressure that your baby makes on the cervix, a bladder or vaginal yeast infection, etc.
For any form of spotting in your pregnancy you should always contact your OB/GYN doctor. Spotting/bleeding can also indicate a more serious condition, like miscarriage for example, or fetal distress, those two need emergency care.
We can not tell you what your individual situation is, so please ask a doctor about your history and the outcome of any bleeding you may face while pregnant.
We wish you luck!