Going from a 14 to a 10

My workout today was pretty good. I was considering doing cross fit but I want to make sure I have good form before I start messing with exercises I'm unfamiliar with at the gym. My husband is going to go over some with me tonight. Instead I did my body sculpting stuff. I wasn't able to complete the workout. I tried. Really I did. But I began to feel really weak. I mean to the point where I just didn't feel like I could do another squat. Even walking over to the area that I do my stretching felt like it was almost too much. It's about 4 hours since I've been home and I still feel a little weak in my legs. I'm wondering if I need to increase something in my diet. I just feel so weak! It could be that I'm not eating enough. It's something to work on. Until I'm sure I'm not going to hurt myself I'm going to stick with the dumbbell exercises in the body sculpting bible. Those at least I know. And I'm pushing myself with them too. So I'm still getting a good workout. Now if only I can figure out why my legs are so wobbly today.