Re:Body parts constantly falling asleep!
I had the same problem. I found there was actually 2 problems, the first was the way I lean on my computer desk with my left arm at the elbow for long periods of time. It didn't go numb then, but for periods throughout the day my left hand would go numb. Once I worked out what it was, it took about a week and it never came back.
The second was sleeping with 1 arm under the pillow and then my head on it. I would wake up feeling like it was someone elses arm in the morning.
Again, changed the way I go to sleep by putting my palms together next to my face on the pillow, happened a few times after, but then stopped and not had since.
When I was heavier, it was a problem in my legs too when I sat on them crossed or similar, but stopped that and it sorted itself out.
Def worth seeing the GP, but if you can work out what might be causing it, change it and see how it is after a couple of days.