Some great advice already given on this thread but I thought I would add my two cents. Just 2 years ago I found myself in almost the exact same position you are. I had let my weight creep up to almost 320lbs (6' tall) and felt miserable and tired most all the time. Played sports throughout high school and college an always was able to eat what I wanted and still weighed 185 lbs, how things change with age
Fast forward 10 years and then combine that with a very sedentary career filled with airport fast food, inflight meals, and beers every night and it was a recipe for disaster. My "come to Jesus" moment was when my doctor had to put me on blood pressure medication at 30 years old and told me if I didn't make a change I wouldn't live to see 40. Combine that with the fact that I could potentially loose my medical over this and not be able to continue my career and my choice was pretty clear, I needed to make a change.
Not saying it was easy and its taken time but I have managed to drop 90 of those pounds and am 30 away from my goal of 200 lbs. I am NOT a diet person at all so I knew I had to do something that would be sustainable in the long run. First thing I gave up was soda...for me this was HUGE. I used to pack down 6-10 Pepsi's a day which alone added up to almost a normal caloric intake for a full day. I limited the processed fast foods to very occasional and can honestly say I really don't miss them at all. My one weakness is the occasional In-N-Out when I'm back in my home state of Cali but that's just one thing I refuse to give up and I keep those visits limited. I still do eat out (especially when I'm out on a trip with work) but try to make smarter choices in what I am ordering. The key thing for me is not getting down on myself if I want to have something which might not be the "best" for me. If I want something I will have it, I just remember to enjoy things in moderation. The above mentioned goes for the booze as well, I still drink but not nearly as much as I used to.
The other major factor for me is maintaining an active lifestyle. I had gotten so lazy that the thought of a gym or even a bike ride would be something I wouldn't have even considered. When I started this lifestyle shift I got into the gym and was going on average 5-6 days a week. I wore a heart rate monitor and would use that to do heart zone interval training (do a google search and you will find a great deal of info on it) Basically, it all came down to a simple formula for me of calories in being equal to or less that calories out. After a year in the gym I found myself getting bored with being cooped up indoors so I got back on my bicycle and started riding again...this for me was the turning point in my weight loss. I started riding 5 miles a day, then 10, eventually got up to 20...I just took it slow. Ended up enjoying it so much that I bought myself a gift and invested in a new road bike. I now am averaging 20-30 a day or about 100-200 miles a week and am loving every minute of it. No doubt I am not the best looking guy in spandex out there but I have found the one thing that I really enjoy doing long term, I hope to keep it as a lifelong passion.
Sorry for the long, rambling story but I know where the OP is coming from...been there and it is not easy. Just wanted to share my own ongoing lifestyle change and give some words of encouragement. Keep it up brother, its up to you to make it happen and there are plenty of us out here willing to lend support to assist you in reaching your goals