I just feel like there's something not right with my body!

I feel nauseous for past 2 weeks, I started my period 5 days ago, I had sex on and before ovulation! I took a pregnancy test the morning my period was due, it was negative and my period came that night, I did a test two days a go , and it was negative!? I haven't been nauseous while my period before, n my breast are sore? And I have never had these symptoms before, something just feels different with my body and I don't know what or why? Help??!!