Bfn 13dpo cd33 100mg clomid days 3-7??

Hi i have been on clomid days 3-7 100mg and i ovulated on cd 20. I am now 13dpo and am getting bfn. I am 2 days late for AF, i have sore bbs, headaches, extream hunger,really sleepy and lots of clear CM which i dont usualy have at this time of the month (Sorry TMI!). Is it still early or am i out of the running this month? Also i am using internet cheap testing strips should i change to a better make?? Any help would be much apreciated!