Taking Provera to induce period

I took provera 10mg for 14 days a month.  1-3 days when finished, it would produce a period.  The first being heavy.  The second month I took the provera again the same 14 days of the month and then a day after finishing I got my period....much much lighter and lasted, very lightly for a week.  Now, on my 3rd month, I took the Provera for 14 days, and it has been a week since I finished the drug and no period.  I am experiencing some cramping, back ache, and nausea, along with constipation.  Feel like I'm going to get a period, but nothing.    
Question:  May I not get a period again?  Has anyone not gotten their period on month 3 ????