You gotta take it easy, a little bit at a time! LOL Seriously, I hope you are okay. It's just like any other exercize routine--you don't start out running 2 miles when you haven't run at all. You start with maybe walk/running a mile, and then when that gets easier, run the whole mile, etc. Same thing with the squats or any exercize. Try doing it a little here and there, and slowly increase the amt of time you are staying in a squat. Don't kill yourself!
You know, be glad that you are doing this now. I did SOME preparation for labor and birth last time, but I was not exercizing during my pregnancy. I had a natural birth that included 3 hours of pushing, and I did a lot of self-supported squats while pushing, as well as reclined squats where I pulled my legs back by myself. My DH wasn't exactly jumping in and offering to help and I was too busy and focused to direct him. He was just there supporting me emotionally. Anyway, after the birth, for about a week, I had SO many sore muscles. Muscles I didn't know I could pull!! like around my rib cage, my legs, and my triceps/deltoids, and biceps. Ouch. It hurt to lean over and pick up the baby since my arms and torso were so sore and out of shape.
This time around I am doing aerobics 3 times a week and also trying to stretch more. I also plan on instructing DH more before the birth and practicing a supported squat with him, and I just read in Natural Childbirth the Bradley Way
that if you pull your own legs back while pushing, to loop your arms under the kneecap at the crook of the elbow instead of pulling with your hands on the outer part of your shin. The latter is much more tiresome, but I didn't know that the first time around!
Anyway, I'm learning from my mistakes and hopefully I can share that with others so they can be more fully prepared. Just think--if you had done all the squatting you did today, but instead for the first time while you were in labor, you'd be in lots of muscle pain the day after the birth!
You're on the right track, and it won't be long till you meet the little one!
PS--Editing to add: Oh, and most of all, I am planning to have a WAY shorter second stage this time around!!