P90x question. Why can't I do yoga x or push-ups yet? I am on recovery week. Please answer.?

I am already on week 4 but I am struggling so much on yoga and I still cannot do more than 4 push ups. That's how many I can do to failure. How pathetic! And I cannot for the life of me do shoulder stance or plow or crane! �And I am a bit better at balance but many moves I can't do without falling. I think it has to do with how much I weigh. About 160.. And I am short.. That's so disgusting I know. I am so sick of it. But still perhaps my expectations are too high. I am not going to quit because I have lost some weight. Not a lot. Maybe 4 pounds.. But after a whole month I expected like 7-8 pounds. I am really discouraged and sad about it. I just want to know if this amount of struggle is normal. I wanna be at 137 by day 90. I was also thinking sense I don't sweat as much as I did the first 2 times I did yoga if during this recovery week perhaps I could incorporate some ab ripper x every other day. I am so sick of this flab! :( or is that too much? I hate this. �Not then work outs. I like the workouts but i hate that I haven't progresses as much as I thought I would.. I mean I new it wasn't going to be fast. But 8 pounds in 4 weeks is not a lot.. Thank you for reading.