Thanks TruSylver and Shawna. Your advices seem to be spot-on. Sincerely appreciated. I will try to be more careful and not starve myself too much.
I just got a book about dieting and it seemed to suggest that the way to go is to increase veggies, fruits and whole grain bread and cut off pretty much everything else (meat, dairy.. etc). This seems to be in direct contrast to what I was doing before. I started to try this today (ate a bunch of cucumbers, tomatoes, apples, oranges... etc, and cut off the meat and dairy).
I also did a 10k run today

My first 10K run in, like, a year. That felt great. Didn't have the power to also do weight lifting afterwards though
My total food intake for today is about 1700 calories. I increased a little bit as you can see