Welcome to HCM,
After going through your history chances of pregnancy
are very very less as your test of pregnancy is also negative,Your symptoms may be due to hormonal
changes just before period,you should get period in a day or two good luck .You may take analgesic
to get relief.
If no period you may repeat the test.
At your age you should pay attention to your studies and carrier,rather indulging in unprotected sex it is risky also.
Please take care.