I have been having a fatigue and heavy feeling in my lower legs for a week now. i do have health anxiety undiagnosed though. what could this be?

It could be: A multiple number of things, certainly anxiety can give you these symptoms as well, however, a physical exam, including neurological exam is needed to tell you what you are feeling. You may need to have some labs done as well to rule out other medical problems with similar symptoms. Get yourself checked by your primary care dr as a start, good luck.