I should have had AF on the 18th April and i still havent had it, if i wasnt temping i would assume i was pregnant but it works out that i didnt ovulate untill day 35 of my cycle and so im now due AF about the 9th - 11th May, i tested anhow on the 24th April and it was a BFN. All i can say is test and see what it says, go with your gut feeling!
Good Luck