The OG needs to be taken before fermentation starts - that is, before pitching your yeast. If your 1.050 was what your hydrometer read after your beer had fermented for a couple of days, then you might have a stuck fermentation (in other words, your yeast has stopped making alcohol).
If your temp. didn't get below 50 degrees, it should still be working strong...unless you're using Lager yeast, in which case you'll be good well below 50 degrees. Really, we all need some more information to give you a real good answer.
More than likely, you're being a nervous nelly and everything is A-ok. The 1st beer I ever brewed - a dry stout kit - only bubbled for one day and then stopped...and the bubbles weren't anything impressive. It turned out to be over 5% and just fine.
Again, knowing what yeast you used, the temp. you kept it at, and when you took your first hydrometer reading. Godspeed! There's a 97% chance you're totally fine.
Agreed - that yeast should be going hungry-hungry-hippo all over that brew! You should be able to hear a slight wooshing sound as the sugar is sucked in one side of the yeast and shot out the other side. Haha! (Just kidding of course - I'd hate for you to be down on all fours with an ear pressed against your carboy )
You should aerate your carboy/bucket. Take a sanitized spoon or paddle and stir the heck outta your brew - really slosh it around! You wouldn't want to do this after fermentation has begun, but if your OG hasn't changed, your yeast might just need more oxygen to do its thing.