7 days late, i don’t know what to do!

So my husband and I are TTC, and we followed the book on conception this month, bbt, ovulation predictors etc... I so thought it was going to work, was practically convinced it had. I have had no symptoms except abdominal cramping on occasion and very light pelvic cramping, and a little bit of back pain, Its now 7 days past my expected period and every test I have taken is negative. I have used 3 different types of tests and tested every day since the 16th. Not even faint lines. No period yet. How long should I keep testing for? My doctor said if I want something to help kick start my period again she would prescribe me something to help get back on track but I am worried about taking anything too soon. Any ideas?