Chefcs5

Ok so I have never ran before. I am trying to loose weight. I started week 4 day 1 today. Normally i walk at 3.8 to 4.0 on the treadmill. I jog at 6.0. I got all the way to the last jog the 2nd 5 min one. I couldnt finish. I didnt give up totally i fast walked at like 4.5 but i was dizzy and legs just were not holding up. Should i go back to week 3 or push on? Thanks in advance.