Hard to say yes or no, given I don't know what you mean by 'unstable'. But I get it's an uncomfortable topic to talk about in the open.
Me, I was really depressed, and didn't know it (and looking back at how sad my comic started out, it kinda makes sense now). Got a recent ASD diagnosis and currently on some meds. Was super high/manic the first week, but leveled out, and I feel like I can focus on doing things I was previously scared or too low to do. I can say that it definately helped boost my work, especially since July.
Guess what I'm saying is it's not a bad idea to get checked if you feel not like yourself and it's affecting your productively negatively. Despite any mental problems, writing/drawing/telling a story should be therapeutic and reflect changes not just in characters and plot, but in you as well. Might not always be happy, or fun (I wrote some boring, depressing sequences myself before i got help), but there will be progress, in your life, and in your writing/drawing/story-telling. It will just take some time to see it.
It won't hurt to see where you're currently at ( getting checked/diagnosis ) cause it'll at least give you a place to start. But that's from my experience.
