Is it possible for someone suffering from constant stress and (ocd) anxiety attacks to have muscle weakness in legs that lasts all day?

Not usually: Weakness in leg muscles that lasts all day would not usually be related to ocd or anxiety attacks alone -- although anxiety can certainly produce all kinds of physical symptoms. Sometimes fatigue can be a symptom of depression and anxiety, though. Please discuss your concerns with your own doctor, who knows you best and can assess what needs further investigation and treatment.

Possible: Absolutely possible because anxiety has strong effects on our muscles and systems. Weakness can be prevalent which chronic stress and anxiety. However this by itself is unusual and i would recommend an evaluation to make sure.