Bfn 3-4 days before af?!:-(

So I'm due for af Monday -Tuesday  and I was so tempted to test not sure why because normaly I can just wait until af! This was our 6th month ttc to our surprise as we've conceived so quickly and easy before. Well anyway 2bfn!!! Only used cheap 99p tests. Am I out???? I've felt so positive this month and really thought it was our month