Don’t be afraid! I was diagnosed this summer (ADHD-Combined), after over 10 years of chronic depression, and a childhood of never quite fitting in. It was *such* a relief to have an answer, pretty much to the entire puzzle that has been my life. I’ve been depression-free for 4 months and counting, and I’m on my way to completing an entire semester of college courses (going into exams with an A+ average!) for the first time since beginning my post-secondary journey almost nine (!) years ago.
Also, there are other conditions that can cause some of the symptoms of ADHD – it’s probably worth the visit to your doctor. Here’s a thought – book the appointment right now. Don’t tell yourself “I’ll do it tomorrow” – there’s no reason to wait!
To be fair, I was certain that I had chronic depression, and “just because…some people’s brain chemistry is like that” was pretty much where all of the various clinicians that I had seen over the years stopped as far as trying to figure out why I was so depressed. I already figured there was something wrong with my brain, so I think that made the idea of ADHD much less scary. For me, it’s a much-easier-to-manage kind of brain wrongness. 
Good luck!