I took a quantitative blood test for pregnancy 18 days after sexual encounter, and a urine test 22 days after. chance of pregnancy?

If pregnancy was established after that encounter it should trigger a positive test by 2-3 weeks. If done early in pregnancy results are more likely to be a false negative than ever a false positive, In time, the placental/embryonic tissues create enough hormones to make tests turn positive.

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.

Yes, you are not less likely pregnant if you have had regular cycle of 30 days or less and both tests are negative.