Mental Health Tests. I go about it?

I have been struggling with extremely low self esteem, recurring migraines and severe anxiety for a long time now. Add that to my bulimia, and I'm a mess. Recently, I've been facing a sense of detachment from my body, and it's almost as if I'm an outsider to myself on occasions, like I'm viewing myself from an external perspective. I spoke to my friend but he says he's never experienced this before, which scares me. It happens very often. I want to take some steps to get diagnosed because not having any answers is bothering me a lot and interfering with my daily life. What kind of tests do I need? Who can I approach for this? I have limited monetary resources, but the least I want to do is get diagnosed. How should I go about it? Essentially if I'm almost 17 and my parents are not aware of this (they don't believe in mental disorders).