I got negative pregnancy test after waiting 16 days from sex(sexually active only in that day). and it was actually my 28th day expecting my period that day having intercourse.so it makes me45 days now with no period from my last one?

Although pregnancy is a common reason to miss a period, it sometimes happens in normal women. A period can be triggered by taking oral hormone tablets you get fro your doc. Most would not go that route unless this went on 60-90 days and pregnancy test remained negative.

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.