I have been feeling very lightheaded as if I am about to fall to the ground and pass out when walking. But there is no actual problem with standing up and walking but still I am convinced I am about to fall to the ground. I also have this weak feeling in my legs and arms like my muscles would be really tired. (but the feeling doesn't actually affect my strenght or anything) Could this be anxiety? I just am really afraid of passing out and that this is symptom of something serious which leads me to get more anxiety. 

(I hope everythig makes sense, english is not my first language)