I'm 16 weeks and feeling the same just tired and my back has been hurting and feel tired and out of breath. Even saving and bending over seems exhausting. My doctor said it's normal since your heart is working harder and just to relax and take it easy when your really tired
That is something you should talk to your doctor about the baby doesnt even weight half a pound yet and most FTM don't start showing until their 5th or 6th month you're baby is still too low for you to not be able to bend over its just bloat not baby bump
You should probably talk to your OB about this. At 15 weeks you shouldn't be incapacitated like this - you are just barely into your second trimester.
Talk to your OB.