Trying to shape up, help?

My schedule is kind of odd from many, I work usually from 330 or 5 in the evening til night and ALL day Sunday and Saturday's. So I tend to eat late, sleep late during the week, etc. I live on my own with my fianc� who has lost weight just from not having money to eat out! So its hard to buy super healthy foods. But I am starting a 7 day cleanse with a supplement to kick start, and then I will start my diet with oxy elite pro. I've used it before and it helped out (with me doing the work of course), helps give me energy and overall helps my appetite. Let me make this clear, I want to make a permanent change. I feel lazy and tired all the time, I get pain in my knees and hips on weekends when I'm on my feet the most, I'm always up so late cause I never get actually tired enough to want to sleep but then I can't roll out of bed Til 12pm. I am 5'9 and about 174 pounds, I'm 19. I've been around 158 before and I have pictures from that time, I miss my clothing fitting looser! It's been a stressful year between graduating high school last year and gearing up for school this fall. I moved into a 2 story apartment intentionally to try and get my knees working daily on the stairs which has helped the pain (I have hypermobile knees so the muscles are very limber), I'm not buying diet soda anymore switching to juices and water, buying bran cereals not the sugary stuff, fruits, lean meats, protien meal bars for my double shifts to avoid eating ITALIAN! I work in a restaurant makes things harder. I buy crystal light as well, etc. What advice do you have for me?! Anything from staying motivated to exercise that will get me fit and down to a healthy 155-160, not so I can wear a size 7. Sizes don't phase me it's what I see in the mirror that I care about. I used to have a bad attitude about my body and never lost weight til I calmed down, but again stress has gotten me this year. No excuses, ready to do this thing so by new years I can make a whole different resolution!!!! :)