Welcome to Health Care Magic.
Bases on the information provided, you symptoms you have been experiencing could be due to Premenstrual Symptoms or pregnancy
Abdominal cramps and breast tenderness as also seen in premenstrual syndrome
. You haven't mentioned about your cycles ( the duration and regularity).
People with thyroid
problem often tend to have irregular periods
.I assume that you have 30 day cycle and regular. If i am correct then the due date of period should be 15 May 2012.
Pregnancy has to be suspected only when there is a missed period. At this stage i cannot confirm the exact possibility among premenstrual syndrome and pregnancy. Just wait for 7-8 days. If your period does not come, then go for the pregnancy test again.You had pregnancy test done too early. Because pregnancy test may give false negative results if performed early , it is better to get the test done 2 weeks of missed period as it gives more accurate results and reduce the chances of false negative results .
Wish you a healthy Life.