Guadalupe, I’m sorry you are feeling so badly. I know that after a few days “in the food” I often can feel quite low and hopeless, which I’m hearing in your post.
I just wanted to point out that you said this, “I was 3-4 days without eating gluten and just lactose-free, and the truth is that I felt better about myself, not only because of having been gluten-free and that, but because I realized that I was without gases, without feeling heavy, without feeling bloated and with poor digestion and a bad taste in the mouth.”
I think you have a big why right there, and that perhaps you can revisit this with a fresh perspective later, seeing that you have a HUGE non-weight motivation, AND that you already know you get that benefit almost immediately, and I’m guessing that if you keep it up, those benefits will not only last, but increase.
I know you can do this.
Try to put these days of overeating behind you because I think you have the answer in your answer!!