I am sorry that you are going through this but you're moving in the right direction by starting to ask for help.
What you describe sounds like disordered eating patterns and thoughts that could very well turn into a full blown eating disorder. I read your story and it took me back to my experiences. I could recite the calorie content of everything in my house and I know what's healthy too.
I also know that somehow it always ended up being too much and then it was never enough. Only, it wasn't about food; I was too much and then never enough. It took me six years to figure out that it was never about food or about my size; it was a coping mechanism (It was my way of trying to control things)...
If you told your parents and they don't think it's a problem then there are somethings you can do. You can go online-we can't give out links to other sites- but there are several sites where you can take an online eating disorder screening.
Most screenings are only 5 questions long. You have pretty much stated 3 of the 5 statements in that one paragraph alone. Print it out and either try again with your parents or try a school counselor or a nurse-don't give up! A counselor can help you with DBT or CBT skills to use.
Some people, like me, wait years and years before reaching out and by then the damage isn't always reversible. Please take the screening soon.