Modifying Insanity

Is there anyone else out there doing Insanity who has to modify it? I have a very difficult time doing pushups. I can do pushups on my knees but I cannot do regular pushups. This was easy to modify in month one but now that I am on to month two it is becoming more difficult.
I did Month 2 Max Interval Plyo today and I felt like I didn't get as much out of the workout because there are so many different variations of pushups. I tried doing the best I could but I still feel like I missed out on a lot. Does anyone have any suggestions for modifying? I still did burn 650 calories according to my HRM but I was really hoping for more.