I have had unprotected sex ever since i have been throwing up had horrible cramps in my lower stomach and have been extremely tired and have had bad headaches i had a period but i don't know if it was a period because it was very light am i pregnant?

Conception occurs within day or so of the sex. It takes about 3 weeks for the embryo to make enough HCG for a positive pregnancy test. Blood test may be done a day after a missed period. Home pregnancy tests should be done 4-5 days after the missed period. If the result is negative repeat the test in 4-5 days. Use first morning urine and follow instructions for the test carefully.