Hi hon! Implantation bleeding happens from 6 - 12 days after ovulation! so 7 - 14 days after intercourse! So at the most there would be a chance of implantation bleeding at the lates the 26th of July! Unfortunately honey, I can't tell you if you are pregnant or not! And our periods can be TOTALLY regular and the same for years, then all of a sudden WHAM they go wonky. There are many factors involved in this change - stress, diet, anemia, anxiety etc. - Do YOU think you ARE pregnant? IF you do, then give yourself till Monday or Tuesday and have your doctor give you a BLOOD test, these are more reliable than a urine test! The urine test ALL depends on the count of HCG, in your case if you wait till Monday you will be 22 dpo (days past ovulation) so that WILL be totally enough time and strength of the HCG to definitely tell! Just know something else, I have talked to 2 other women on here that took HPT after HPT and it said negative, both had blood test that showed negative, but they were both pregnant! So it is best to have your blood taken at your doctors office, both of the women I talked too had theirs taken at the hospital! And since your only time of having unprotected sex was on July 12, this should be dfinitive if you are or aren't pregnant. So let me know OK? Good luck honey!