As with any verb, it depends on the context. You have to use the infinitive form and say "I used to binge watch a lot of Netflix" as you could not say "I used to binge watching". Similarly, the gerund phrase would take precedent if acting as the subject of the sentence. "Binge drinking is a serious problem with today's youth" as opposed to "To binge drink is a serious problem with today's youth." In short both are completely acceptable, depending on the surrounding grammar and context.

The verb phrase "binge eat" isn't as common as the noun phrase "binge eating", but it definitely exists. I've heard it used. The Oxford Dictionary even has a listing for "binge-eat", though they spell it with a hyphen.

The more common and widely accepted phrase is "binge eating" rather than "binge eat." "Binge eating" is the correct term used to describe the act of consuming large amounts of food in a short period, typically accompanied by a loss of control overeating. It is important to use the proper terminology when discussing eating disorders or related topics. The phrase "Get back to the you when you go to school" doesn't sound natural and might not convey the intended meaning clearly. If you want to express that your friend has changed in a negative way and looks worse than before, you can use alternative expressions such as: "You've really changed since we were in school." "I've noticed that you're not the same as you used to be." "You don't seem like your old self anymore." "You've gone through some changes, and it's not for the better." "You look different now, and it's not in a good way." Remember to approach such conversations with sensitivity and empathy, as discussing someone's appearance or personal changes can be delicate.