I had sex 20 days ago no period and a thick mucus with brown and cramps all pregnancy test say negative could i be pregnant? should say by now right?

Possibly: Repeat the home pregnancy test. If its still negative, see your doctor and ask for a serum quantitative HCG test. Anything greater than 10 miu HCG is considered positive for pregnancy.

Could be: 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.