Thank You. I've Been Trying To Lose Weight, I Need

Thank you. I've been trying to lose weight, I need to lose a lot, and although I try to be more active, and not eat to late, and cut down on portions, it won't go away. I'm beginning to think it may be something else. maybe my thyroid is out of wack. I'm male, 6'3" tall, Caucasian, over 375 pounds. I'm out of breath a lot from this weight so it makes it even harder to keep moving. It's almost a Catch 22.