How to get a half decent career with only a high school diploma?

I have a high school diploma, and I took classroom instruction only forklift safety just to add something to my resume. I used to work at a golf course picking up golfers golf bag, cleaning golf clubs and power carts, I also work at a sports facility on call doing cleaning, minor repairs and working special events. I recently started at a warehouse owned by irving, but I hate it so far since the minor workers (those that don't have the green shirts) have a hard time doing the hand packing and the managers (green shirts) keep sending people home even though we need help doing some of the packing. I just need something half decent that I could do, I know I stuck around more than the average person since the average worker stays for 3 days and I am going on day 5 friday night (I also rotate between day and night shifts, I do 2 days, 2 days off, 2 nights, 3 days off) and when I asked for the same shift, they said they could make it happen, but I would only work 2 days a week, which I cannot afford. I work 48 hours a week (12 hours a day) and I make 9,40$/hour (minimum wage is 9$/hour) and I will stay at 40 cents above minimum wage whenever it goes up. I knew it would only be temporary when I got in, but I am not sure I can handle the long shifts with no sick days, no breaks, no nothing except work right through the 12 hours, I want something a bit better than hand packing for a life