Why am I feeling like this?? Any advice?

I had unprotected intercourse two weeks ago. I was due for my period on the 10th but I got it on the 6th (4 days before). My cycle is always normal, so I didn't know what to think. Everything seemed normal until yesterday, I"m not bleeding as much as my normal period, but its still more than they "say" implantation is suppose to look like. I had a headache all day and I feel it coming back now. I've been having a lot of nausea, since yesterday morning, and just feel sick to my stomach. I took a test this morning and it was negative. Any advice???Why am I feeling like this?? Any advice?
Take another test and see your doctor. they can give you blood work to see if you are truly pregnant or not. Those store tests are only 99.5-99.9 percent accurate. the blood tests are 100% accurate. Talk to your partner: did he ejaculate inside of you?
Your period isn't always going to be the same. it varies depending on your body and weight so don't worry too much about that. If you are still worried, talk to your doctor and next time, use a condom or some other type of contraceptive.
Take a test again, you might be pregnant.
Having unprotected sex could be weighing heavy on your mind, so I doubt it's pregnancy, but more likely a lot of stress.
Always double check, and take another pregnancy test. If it's negative yet again, I would just assume you're stressed out quite a bit and need to take some time to relax. Your period always changes along with lifestyle changes, so don't be too alarmed.
Best of luck.