How many days after unprotected sex should i take pregnancy test? my period irregular?

A known exposure that leads to conception can trigger a positive pregnancy test by the third week after that encounter. Urine pregnancy tests are more often falsely negative early but rarely falsely positive. A first morning urine is often the best source for testing.

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.