Could she be?

Well me and my wife have had sex in the recent weeks and this may be weird but I know my wife period like clock work, my problem is here period hasn't came like it always has, she told a pregnancy test and it came out negative but my sense or my "Jedi" hasn't went off about her period and several family members recently let me know the same thing happen to them, my question is that should I be on guard that she might be preggo? Or should I not be?