The weight is melting away

I have never really struggled with my weight until about 8 ish years ago. I gained about 5-10 lbs when I had a job as a coffee truck driver for a couple of years. Sitting, driving, eating cookies. Then my weight plateaued for a while. I gained a few more pounds over the next couple years. Then I broke my leg. I think I gained 10 lbs in 3 months while I was healing. I was 172 when I started walking again. I decided to go on a diet. That lasted a couple of days until my mom took me out for lunch. I ate a legendary platter from white spot. When I logged it I found out it was something ridiculous like 1900 calories. Instead of just moving past it I gave up. I gained 8 more pounds in the next 15 months. The scale just hit 180. That was it. Now I'm watching every calorie. I have lost 4 lbs in about a week and a half. I don't feel hungry or bad. I am careful to eat 3 meals a day and even a snack after dinner if I still feel peckish. My calories​ goal is 1640 but about half the time I still have 500 or 600 still remaining at the end if the day. Which in theory tell me I am not eating enough, but I feel good and don't feel deprived of food at all. I am wondering if this is maybe just water weight coming off first, then the fat will go after that? Then maybe my weight will even out and slow the loss?