Is it normal my arms and legs are weird?

You probably have early osteoarthritis or something from being severely malnourished. Eat a balanced diet and see a doctor if you weigh so little. Maybe you have a problem absorbing nutrients or an eating disorder. I hope you find help, things will only get worse if you don't figure out and work to solve what's causing these issues.

Are you anorexic, or bulimic? You sound like you are so severely malnourished that it's starting to affect your joints, and that's not good! You need to see a doctor ASAP. I couldn't help noticing that you said you weigh 72 lbs, and that's not normal for anyone who isn't a little person.

If you are 4’ 10” or taller, you are way underweight at 72 pounds. Joint popping and stiffness is not unusual for underweight out of shape people. Same with feeling fragile. If you have persistent joint pain or swelling (you’ll normally feel some pain right when a joint pops), that’s something you need to see a doctor about. Otherwise, put on some weight and do light stretching regularly. Also, stay hydrated and make sure you’re getting proper nutrients.

Eat eggs and drink milk.

How underweight are you?

I weight 106-110 and I occasionally get this. I have to eat a lot just to maintain my weight.

I recently started drinking muscle milk and it is really helping. It's expensive but the protein is helping a ton as are the fatty acids.