Keep gaining weight. Please help, I'm just so frusterated.

I was wondering if anyone has anything that can help. I keep gaining weight. I have been heavy most of my life. I am in my late 20s and I weight about 350 lbs at 6', I lost over 100 lbs on Atkins but I felt terrible. I don't even like meat and I was vegetarian for years. When I was vegetarian I was probably 220ish and maintained that fairly steady. I started meat again and gained and gained until I was almost 360. I started Atkins and got down to about 250 lbs. I felt so sick all the time and my liver was physically hurting. So I was like I cannot do this anymore. I went back to vegetarian, but I am gaining weight like crazy.

I eat anywhere from 1,400 - 1,600 on most days. Generally for breakfast i have fruit and hot tea (no sugars). Fruit varies by day, but sometimes a grapefruit, a cup of grapes, some berries, or something like that. Lunch varies some too, but a frequent one is cooked spinach, red beans, and brown rice. Dinner varies too, but it might be about a cup of cooked quinoa, some hummus and carrots, baked cauliflower and Brussels sprouts, and black beans and jalapenos. If I am hungry between that, I'll get something like carrots or radishes and hummus (I make it and use very little oil) or berries, occasionally raw almonds.

I walk on the treadmill about 3-5 miles. Only maybe a mile of that is jogging. It's hard with my size. I do yoga for about an hour. A few times a week I have 15 lb weights that I use. I do as much of a sit up as I can for as long as I can, normally only 30-35. I can't do any pushups that aren't the "girl" pushups (I don't mean that in an insulting way, I have no idea what they are actually called, that is all I have ever heard). I park in the farthest spot at work, I get up and walk around the campus several times a day (fairly large university campus), and I always take the stairs.

I'm just so frustrated. What am I doing wrong?? My thyroid isn't the best. I take 90 mg of armour thyroid for the past 5 or 6 years now. I haven't had it checked in about a year because my health insurance sucks something bad and I am a grad student living on almost nothing.

What else can I do? What should I cut from my diet? What else can I do to exercise to help? I am just so depressed. I hate myself. So much. I have always been the fat ugly girl. I am sick of mean comments. I am sick of how people treat me. I'm sick of people acting like I am eating nothing but pizza and cake all day. I can't remember the last time that I ate pizza or cake or "junk" food in general. I cook at home 99% of the time (business lunches that I just can't avoid, but limit to salad or luckily often they have hummus and veggies!).

I will literally take any advice, just please don't be cruel. I know I am gross. I'm trying.