I took clomid for 3 months and it made me late every month. It made me ovulate later and therefore made me start later. My cycle was usually 30-31 days long and it made me go till cd35-36 days or later till around cd37 on month. Kinda stinks though because I was hopeful being that late BUT it made me late and of course AF showed. :( I hope this isn't the case for you but just letting you know my own personal experience. Good luck hun!!
Clomid makes your cycles a little longer. everyone I know that has taken has said that it was aleast 5 days late if it didn't work the first round. I was a first rounder so I'm not sure what to tell you.
I am not sure about the pregnancy thing.
I also have endo and my re will not let me be on clomid because he says he makes endo worse!!!