My arms and legs feel weak, like they our lacking oxygen. For the last 4 months, yet I can breath pretty well my chest.

No oxygen to legs. Even though you fell like you are breathing well you may want to get the circulation oxygen supply to your legs checked out .Especially if you have varicose (swollen veins )which may nit be caring oxygen to the muscle in your legs , the test is easy called venous doppler study.