sometimes your levels wont be high enough yet for it to show up.. everyone is different! wait a little longer usually 2 weeks past your normal time you get your period... periods can be affected in many different ways, stress, being around a new crowd, etc. it may just be late... if you get too worried call your doctor to get blood work that'll definutely tell you whats going on!
wait for like more 3 to 5 days than take one more hpt.