Weigh much more than i look?

i weigh 400 pounds, yet i look to be about 300 pounds. I have lots of fat hanging off of me. I look waaay smaller than all of the other people that weigh this much but i seem a lot softer. My question is what does this mean in regards to my frame size and body somatotype. I definately get fat easily (an endomorphic trait). Yet i am tall, have broad, square shoulders that are wider than my hips and i have no trouble with losing weight when i remain active (mesomorphic traits). Just interested because I am about to embark on a weight loss endeavour and I would like to know what kind of body might lie underneath all of this insulation.