My partner and I started having unprotected sex on the 4th-16th and my breasts became tender and swollen.On the 19th I had my period but it differed from my normal period because it was light and it lasted 3days and I did not have any period pains.My normal period lasts 5-6days and I have very heavy flow,and I also suffer bad period pains.My breasts become tender during ma period and after my period the tenderness disappears.Its been two weeks since I had my period but my breasts are still swollen and tender.I have felt tired these past days,I am constipated and sometimes I become nauseas which results in me wanting to eat but I have now thrown up yet,I also get slight headaches and dizziness.I took a home pregnancy test 4days ago but it was negative.What can be wrong?

You could have just had an off period. You also could be testing way too early for a positive result if you are pregnant.

I'd wait for your next period. If you miss it, or it's off (periods stop during pregnancy, but some women do experience bleeding during pregnancy) then try another test. Make sure to use first morning urine when you test, it's the most accurate.

I will do so,my periods have always been regular and I have never had an off period.Thank you for your response.