It could also be a problem with blood vessels in your legs. Smoking Marijuana can increase heart rate and blood pressure. You could have weak blood vessels in your legs and if your blood pressure increases it puts extra pressure on those blood vessels. If this is the case then it is possible that if your blood pressure increases too much you could have more serious problems. If you've never gone to a doctor about it then you should. More than likely it is nothing serious, but better safe than sorry.
Why do my arms go numb or become tingly and painful when I sleep? And how do I stop it? (and it's not from laying on them)
That is almost definetly poor circulation in your arms. By being awake and moving your arms you increase circulation, but when you're asleep circulation is reduced. This is also the reason people's legs fall asleep when sitting for long periods of time, not enough blood flow is getting to the nerves. How to stop it, well I would go see a doctor and they could easily give you meds to increase blood flow. If you are overweight then loosing a few pounds could help. Also you can try stretching and shaking out your arms before you go to bed each night. Eating foods that can help circulation could be benificial too (hot peppers and tea are great). Also, there is a supplement called "folic acid" which is supposed to be good for your heart and circulation.