I had sex about 5 weeks ago a week after that I spotted 1 time when I peed for two days after that I haven't bled at all. Ever since then I've been feelings nauseated after eating certain things even vomiting after smoking. I've been bloated, headaches, fatigue, enlarged and sore nipples , sickness. I've also been very emotional and sensitive. Also been having weird food cravings . I took two pregnancy test both came back negative it's around the time for my period now but I haven't had one. My period is also irregular. I took the test before a missed period. Please HELP! II'm so confused. I'm also 18

Really too early for a valid test.
You need to be about 2 weeks late to properly test, and then do the test first thing in the morning, as soon as you wake up.

Or go to the doctor now for a blood test.
You can have pregnancy signs for many reasons, My wife has had them for two months due to body chemistry changes. Yes we went though all the testing worry also.

And even the most regular people will get a off month now and then, due to changes in health, stress and more

The longer you wait after your period is due the more accurate the test results. It is still too early for physical symptoms to manifest even if you are pregnant.

I would wait at least another 2 weeks before taking another test.

With irregular periods to start with, it can be hard to know if it is just an off cycle or due to pregnancy. Given your possible symptoms, and how long ago that you had sex, I would either test again in a few days or just go to your doctor's to see about having a blood test.