Very faint BFP HPT but feel like AF is about to arrive?

Hi girls - I have just asked a question about BFP. I took a test this morning as I have been unbelievably exhausted and dizzy but thought it would be BFN as I have been having achey crampy feelings - I got very very very faint BFP but I cannot help but think AF is still going to come!?!?! It does feel a little different - basically everything aches is this normal?