Negative Pregnancy test??? Pregnant?

OK well my husband and I (TTC) had unprotected sex for 5 days and on the 5th day i had my period. It didn't last as long as usual. Its been about 3 and a half weeks and im having a lot of symptoms, headaches everyday, sickening feeling, lower tummy pain, vivid dreams, breast feel fuller, dark veins on breast, some bloating and some acne, and some lower back pain. I took a test today and it was negative.. Did i test to early? Could i be pregnant?