"maybe I've also had this underlying feeling he marryied me to get a visa."
I think this suggests you feel, on some level, that there is something not quite right with your marriage and set up. And I would also suggest that this has possibly fuelled your weight gain.
It's an odd thing, weight gain from overeating. It's often part of a wider net in your life that you are caught within, made up of lots of strands of unhealthy and unempowering habits. My personal perspective is that those habits arise out of developing a coping strategy for a life or a set of circumstances that are not optimal for the person you really are.
The thing is that you know you want to lose this weight. And that want, that desire, is a powerful tool. But you need to own it. You have to grasp the idea that you want to do this for you, not your husband or your marriage. You have to feel selfish about it.
Unfortunately, I think the situation with your husband is somehow stopping you taking ownership of this desire on the deep level you need to and stopping you from making the changes to your lifestyle that need to be made.
I'd suggest that you might find morning pages a good place to start figuring out some of this stuff. All you need to do is just free write three pages a day, filling the page with any old crap. After a few days, you'll notice that odd things start to come to the surface. It's a great way to get rid of buried emotions and sentiments.