Question about clomid

Marissa • My name is Marissa I have been married to my husband Walter since March 25 2014, and we have been TTC for 3 years.

Hi, I was on femara for 3 months with no luck this cycle my ob put me on Clomid which I took day 5-9. Right now I am on day 13 I am still getting negative opk's and have no CM what so ever. This did not happen on femara. Is this a sign of Clomid? I ovulate regularly and by this time I would of had a positive opk. Does Clomid cause it to come later? And is it normal to have no CM? Thanks