Thoughts?

AF was due back on May 5th and it is now May 18th and she is still no where to be found.  I have been super tired lately and the last two days my stomach has been achy (but not nauseous).  I took a hpt on May 7th and one again on May 12th and both were negative. They were the walmart cheapy kind, if that matters. Is there still hope or is it more likely that AF decided she just wanted to go on vacation this month? Hubby and I have been TTC for 7 months now with no luck and I am so wanting my BFP! :(