I've switched hobbies like you describe--buying the "stuff" to start up, trying it for awhile, maybe even a class or two but kinda fading out on it after awhile. I'm a lot lot of things but bipolar's not one of them. I think anyone searching for a sense of self/usefulness/purpose goes through things like this. You did it all frugally, so it doesn't sound like a manic spending binge.

I'm wary of any T who seems to be too hung up on a preconceived idea. If more than one trusted source said, hey you seem to be manic, then yes you could take it more seriously. But if it is only one person saying it, it is understandable to be skeptical.