Congrats on losing 70+ lb already, you should be proud of yourself for getting this far, and I'm sure your determination will carry you through to your goal weight (with a little help from our old buddies Diet and Exercise, obviously).
If you're not happy with your weight, then you need to tune out the people who try to make excuses for it, and just do what you think you need to do. I've had people tell me that I'll never be thin "because of my genes" or because I have a "heavy build", but a lot of the people who made those comments are also overweight, so I have my doubts about their motives.
Good luck with everything; hope to see you around the forums.