Hi, I am a mother of two, my youngest is 6 months old. I started a regimen of working out at least four times a week for 45 minutes. I have been mainly using the eliptical and treadmill with a combination of some step classes. I have also been trying to cut back on my food intake. My goal is to tighten my abs, build my legs, they are flabby and skinny. I would also like to lift and tighten my rear. And tighten my arms. Should I be taking something to help build the muscle in my legs. I have always had skinny legs. I have started to do squats once a week with ten pound weights. Some please give me advice.

I wanted to add that I weigh 133 pounds and 5'4.

You can eat almost as much as you need, you should never feel hungry. Just eat clean: tuna, chicken breast, etc.
Your regimen sounds like a pretty good one, just do your best to stay consistent.
Drink lots of water. Excercising first thing in the morning will also make your metabolism skyrocket.
Hope this helps.

If you want to build muscle (which is the only way you can increase the size of your legs while making them firmer and more shapely at the same time) you must gradually increase the resistance by adding more weight and getting stronger. The best exercises for this are the basic compound movements (movements that involve more than one joint), like squats, deadlifts, military presses, bent rows, bench presses, etc. You need to get a basic adjustable barbell and dumbell set, so you can do these exercises.