My 2002 nissan altima 2.5s does not go into reverse...?

While i was on the high way my car turned off. I checked the trans oil and motor oil but it was empty, however the interesting part was that about 3 weeks ago both tanks were fine. Why is it soaking up the oil so quickly? My car locks back and it only runs well if i continue to refill the trans tank. Then that same day it didn't want to hit reverse. What is happening to my car :(? help!