I am 24 weeks pregnant and i walk as much as possible after resting and i get up to use the restroom or walk a couple feet my knees hurt. why is that?

Take a break: You've heard the old saying, if it hurts, don't do it. In pregnancy, all of your joints are weaker, putting you at more risk of injury. If you are having pain, back off a little and see if it helps. Rest when it hurts. If it gets bad, you may need to see an orthopedist, but I can tell you from experience, they don't like doing anything with pregnant patients if they don't have to.