Don't be so pressured to try and find a "label" for what ails you. It may "seem" to help to be able to vocalize and isolate a problem (or series of problems) that you're having, but realistically what you're doing is leading yourself down a road to "self-diagnosis" (you could potentially "diagnose" yourself with far worse things, and it will only affect your mood more intensely).

I would say continue to make art. Express yourself. Whatever you do (regarding media of your artwork), if it's not relieving you in the way that you hope, try some new medium for your art. I moved from music/performing arts to visual.

I would theorize that your doctor/other specialists are hesitant to "nail down" their diagnosis for you because you are so young. This disorder generally fully develops in the late teens/early 20s (mine fully manifested around age 19/20).

I would also suggest that you address your family to get the point across that "there is something wrong with my mental health and I need to be evaluated for it". Don't immediately jump to a few conclusions you pulled from WebMD or this site; that's not what they're for (especially for mental health issues).

This is at least what I wish that I would have done if I was your age again. I could have saved many relationships and attempts on my life. I won't lie to you, teenage years (especially for someone with an issue with their mental health) are some of the most trying years in one's life. Just persevere and if your relationship gives you support to help you through, then continue with it.