Sex then plan b right after. and a negative pregnancy test 9 days later i believe,she got cramps the day after sex and has had them for 13 days now... could it be pregnancy?

Suggest repeat pregnancy test via serum HCG, as "9 days after sex" is too soon for a home test to be positive.

HPTs are accurate about a week after a missed period. Nine days may have been too soon. Has she missed her period? If so, test again.

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.