If I'm doing my math right you are about 24,or maybe a little less. I'm not a fitness expert, but I know what its like to be out of shape As many have said , you need to start off slower than you initially have. It won't take long to figure out a speed you can maintain, yet not leave you foaming at the mouth. I think you can spice things up a bit if you want by pushing hard up hills, or maybe cranking up for half a mile to spice things up, just let yourself recover. I think you can take it... Ah.. to be young again