Weight loss plateau...Overtraining?

Hi Im a 25 year old male well muscled 6 foot tall.... working a job where i walk on average 10 miles a day. I get no days off working 6 days a week nonstop for about a year. When I started the job I was very heavy...let myself go...i was 310 pounds ususally my good weight was around 200 pounds....in about three months I lost 60 pounds and am currently at 250...but i am stuck and can't lose anymore no matter what I do....I have cut out most bad foods.....usually eating toast and a yogurt for breakfast....protein bar for lunch with water...snack on beef jerky....and eat rice and chicken or a sub for dinner.....i have the odd candy bar or coke once in a while but nothing crazy....Recently I have experienced increased anxiety and depression....i supplement with ginseng b vitas multis glutamine and a few others..but mainly im asking if anyone has experience with this problem.....is it overtraining...slow thyroid? adrenal burnout? high cortisol?....i have a lot of anxiety in my family background and have slow thyroid in family as well....got it checked when i was 18 and it was fine.....Anyone have any ideas...please help!?