The answer is "or what, but." I am an engineer, or at least I'm capable of wearing that hat. I am also a thousand other things. (Mark Penner introduced me to that TV show by saying "You know, you're basically Jarod.") Simultaneously and contradictorily able to wear many hats and be many things without really being any of them.
And that's okay. I'll fit into many classifications but never really stand in any. (Maybe the closest right now is "engineering education," but that's leaving out a lot - the dozens of disciplines that feed formally into that, and the thousands of random snippets that do.)
Brian Bingham was right: all models are broken, including our models of trying to classify people as certain things. It works better for some people than others; some folks can collage the existing models to make a simulacrum of something close to them, but to quote Brad Minch: "The best model for a cat is a cat. Preferably the same cat." /s/cat/Mel. This is likely true for all people.
I'm still struggling with my need to feel that my life is "valid" - not just valid, but "respected." The culture of engineering seems very centered around the notion that technical superiority (or the technical and nontechnical abilities you need to execute technical things, rather) is the basis on which a meritocracy ought to be based. Other things are good inasmuch as they honor, understand, and support this - it's a form of imperialism, like when Western cultures become fascinated by Aboriginal tribes because of "what their primitive ways can teach us." (Grossly exaggerating and oversimplifying here, but I feel at least a slight undercurrent of this sentiment.)
I love engineering and technical things. I also love the pure mathematics and sciences, the social sciences, and the humanities, but while it's perfectly all right for engineers to have those "as hobbies," I still feel a stigma at the thought that I might like them just as much, or even more - that engineering may be my "hobby" and something else my passion. (Engineering education, again; I never feel so alive as I do when I'm working on engineering education - at least right now.)
The lack of methods for formal approval of the kind of life I want to live (...which is a life free from the constraints of formal approval, so yeah) means that I'm often ridiculously underconfident and often think I'm doing something terribly wrong because I don't fit into any of the million predefined slots.
This metafilter post ("I landed my dream job but don't think I'm cut out for it") perfectly encapsulates the way this underconfidence coupled with my desire to please makes me absolutely terrified when I'm working. That's a dead ringer for most of the projects and internships I've had - and they've been great, but I've never been able to shake that fear when I'm working. Thankfully, the MeFi community has some great suggestions on how to cope with it as well (the kinds of things you sort of knew already, but that people still need to tell you to do sometimes).
There is a fine line between being brave and visionary and being stubborn and narrowminded. I never want to blindly charge into a lost cause because I'm too thickheaded to ignore the cries of wisdom around me. But I don't want to be swayed into doing something that's not my calling because of what other people say. I'm sure that 60 years from now I'll look back on this and laugh, but hindsight is always 20/20 and all the meandering paths you take culminate in coolness in the end somehow - you just don't know what that will be when you're stumbling around in the myopia of youth. (I always found it ironic that as the vision of your eyes degrades, the vision in your mind that counts is sharpened.)
But I'm me. And that's okay. And I can be the best Mel I can be, so I will. And that sounds very stupid when I say it out loud, but it needs to be stuffed into my head.
This is a continuing struggle. It has been for years. It will be for years to come. I need to keep reminding myself of these tiny glimmers of epiphany.