help!

Is there anyone who is willing to help me get into better shape?! I am in the Army and was kind of a PT stud, but just got back to my home state and became lazy again. I have no motivation. I tried working out once. Went from getting tired after 60 push-ups to tired after 20. Went from running 4 miles easy to 3/4 in nine minutes. It's actually scaring me. I'm also 18 and just moved out. So if anyone could help with cheap healthy easy meals and be a free personal trainer, that would be amazing!!