I felt the same when I first 'came out' with my mental disorders. My close family knew and a few friends and thankfully, they were all supportive and very few people treated me differently but my wider friends and family circle and acquaintances didn't know.
At first, I posted anonymously in MH related forums and even on TSR and I noticed there was pretty much nothing but support, both from fellow sufferers and non sufferers on the site. You do get the occasional troll comment like "have you tried just not worrying?", "here you are moaning about these 'conditions' when there are people dying out there of cancer", "you're only making this up so you don't have to work" and things like that and it can a bit little hard to deal with it at first but now I can take it with a pinch of salt.
A few months of doing this gave me the courage to come forward as me and not an anon poster and I even publicly posted about it on my FB page, where at the time, I had a lot of people I didn't really talk to any more and to my surprise, there was even more support. I got so many mails saying people we suffering from the same or similar problems but were too scared to come out with publicly and that me being open, gave them the courage to do so too. These were people who you would never think in a million years had a MH problem. They were beautiful, rich, in happy relationships etc so that goes to show anyone can suffer from a MH health problem. Those illnesses don't discriminate like we do.
I do recommend opening up about your MH problems but only when you are ready. When you do feel ready, I do agree starting small would be a good step such posting anonymously and stating your conditions and see the reception you get and if/when you feel ready, start a blog or come off as anon on sites but only if you feel ready. There's no need to push yourself. If do you start opening up, I hope it helps you like it did me. There's something about writing (or typing) out your problems that can go a long way and that can also help others suffering too.
I personally believe that being up front and honest is the only way to tackle mental health stigma. Its hard, I was so ashamed of my diagnoses, not just a little bit, I felt pure shame so opening up anonymous or as me, was a huge step at first but it got easier each time as I realised I had nothing to be ashamed about. Only those who don't regard MH conditions as real or serious are the ones who should be ashamed. Through being opening I have educated a lot of people close to me on actually what these conditions are and their misconceptions are now gone which overall is what has to happen to make MH illnesses recognised and remove them from being a taboo subject.