Hi, and thanks for your medical question on eHealth's Ask a Doctor forum.
If you were expecting the period around 28th of October and had unprotected sex from 10th onwards, there is a chance you could be pregnant and what you had was implantation bleeding. You took two pregnancy tests. If one was positive (you have not mentioned the results on the other one) and other negative, get a blood test done to rule out pregnancy.
The other possibilities for spotting before periods are hypothyroidism, cervical dysplasia, cervical polyps, cervicitis (infection/inflammation of cervix), vaginitis (infection/inflammation of vagina), cervical and uterine cancer, uterine fibroids, hormonal imbalance as in polycystic disease of the ovary, use of blood thinners, genital ulcers, STDs and stress.
Nausea, headache, back pain, random hot sweats, and increase in breast size can be seen in in polycystic disease of the ovary. Since a confirmed diagnosis cannot be given on net please discuss these possibilities with your gynecologist once. Hope this helps. Take care!
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