Its really weird isn't it. When I first felt that way it freaked me out a little. I almost went to the ER because I thought something was really wrong. But I've heard quite a few people say that it's a common pregnancy symptom. I'm a physical therapist and I have no idea what causes it.
That's exactly like I feel!!! It's like I have the flu or something but I don't :/.....
My legs have felt like that too. Sometimes when I'm walking I feel like it takes every bit of effort to put one foot in front of the other and sometimes I feel like they're just going to give out underneath me and I'm going to fall.