Ovulation on Clomid

I am on my first round of Clomid, days 5-9.  I've been using an OPK since day 10, it's now day 16.  They have all been negative so far.  Is it common to ovulate very late or not at all on Clomid?  I have PCOS and hypothyroidism and my hubby and I have been TTC for 7 months now.  My cycles are extremely irregular at best and usually non existent (like I can go years without one).  My dr put me on provera last month though and it worked.  Anyone else experienced this?  Thanks!