Do I have an eating disorder?

I was a pretty good weight two summers ago. Then all at once, a bunch of incredibly stressful stuff happened (my dad's affair, my own toxic relationship, and my cat's death). I ended up gaining 22 pounds total. I'm 5'2".

This year I've managed to take off 10-15 of those pounds, but because of some thyroid issues and other stress, I've sort of fallen off the bandwagon ... I've only gained a couple of pounds back, but I haven't lost any weight in over a month, and I think I'm starting to develop an eating disorder.

When I'm at home, I do pretty well, and sometimes I just barely eat enough; that is the perfect amount, according to healthy standards. But when I am with friends or with my dad ... especially when my dad takes me out ... I lose track entirely. I eat what I want, and tonight was the worst. My dad took me to a Mexican restaurant and I ordered more than I could eat, not realizing how big a tostada would be. But even though I wasn't raised on this philosophy, I felt somehow obligated to clean my plate, and so I did. I'm nearly doubled over in pain right now because I ate way too much. And even as I was eating it, I was planning how I would cut back on food for the next 3-4 days to make up for this.

The basic idea is this: I feel like I have to hide that I'm trying to lose weight, so when I'm alone or at home (I live with my mom, just the two of us) I do well, but I "hide" my efforts to lose weight by pigging out around other people. I usually feel awful afterwards, physically and emotionally. I don't make myself throw up, and I don't WANT to have an eating disorder ... but I can't pretend that that hasn't crossed my mind.

Is this an eating disorder? What can I do to stop the vicious cycle? I need some help :( this isn't going to fly when I go to college to be a nutritional consultant in the fall :( someone help, please! I don't know what to do.