Art Major to Physics/Applied Mathematics, Advise? Firstly, I'm yet unfamiliar with the query conventions specific to this stack exchange. If I've improperly tagged or placed this question, such that it need be closed or held, I apologize.

Continuing, I'll be brief (To be so, I will mostly omit the anecdotal lead. At anyone's request, however, I'm more than happy to explain.*):

I'm 21. I dropped out of art school during 2016, have graduated high school in 2015, returning in 2017, getting expelled a week later, enrolling in community college classes a few months later, dropping out some weeks later, enrolling at and attending a second art school in 2018 (spring semester), flunking out of my financial aid and scholarship.

A series of events brought me to physics and mathematics. Manic obsession mildly describes my rapture. 

I have dreams, lurid, about sequent calculus. I'm a quite, quite well-practiced autodidact. I read a lot. Springer's (among many others') Graduate Texts in physics, mathematics, computer science. I have exhausted all of MIT's Open Courseware offered for physics and mathematics at the undergraduate and graduate levels. 

I have realized only how little I know, how far I've still to go -- the limits of autodidactic way.

I have pre-calculus -- twice. I have never taken a physics class. (1: Understanding MIT's 'open courseware,' by some, are considered 'course', I'm using the term strictly for that of a credit granting environment).

I need to earn a PhD. I need to participate.

The dilemma: Getting in the door. I, no matter how competent or incompetent, have nothing to show for it. I'm clearly not a competitive candidate (if not an all together joke) for any undergraduate program of the formal and/or physical sciences.

The question(s): how, given these circumstances, can I (be it conventionally or unconventionally) become competitive (at the undergraduate level of the US college system)? If that is too subjective - where might I find resources, if they exist, that will best allow me to answer (successfully) the above question? 

I acknowledge the difficulty, and surrender to the patience it will doubtlessly require. 

Thanks much for your time.

p.s. again, autobiographic details by request
If you have taken courses in Coursera and are comfortable with continuing doing so, you can actually get a degree through Coursera. Here is one option. I do not know whether you completed any courses, and if you did, whether they can be counted towards that degree, but it should be easy enough to find out. 

I would focus on getting a relevant bachelor's degree. No (reputable) university I'm aware of will take you into a graduate program without one. 

Good luck!