Why is my body betraying me???

So Tuesday I caved, I couldn't hold out any longer, I decided to join the masses and get a gym membership. I had been wanting one for a while now, but it is just so hard for me to spend any money on myself, and besides, I have a treadmill at home. Why do I need to use one at the gym? I was super excited to go to my first class, I chose Body Conditioning. It is basically a class using free weights to "tone and define your body". It was so awesome!! I left the gym with that great feeling, you know, when all your muscles are shaking and you feel that you may collapse at any moment. As the day wore on, My legs started to stiffen up, but it wasn't so bad. I had planned on going to a spinning class the next morning, but when I got up, I was not not moving very well. I didn't want to embarrass myself in the class, so I skipped out. This morning I planned on going back to that same Body Conditioning class, but due to the fact that I can no longer move my arms, I decided against it. So is this what it has come down to? One great workout a week and the rest of the week recovering! I don't consider myself weak, but this last week has me reevaluating myself! Who knows, maybe my body will get the hang of things, maybe it won't. But, in the mean time, I will hang out with my new best friend, my heating pad. Ha!!