Hi @jem80,
I know what you mean. I have had around 15 years of experience in concealing my mental illness form everyone I know, including work colleagues, friends, family and acquaintances.
The good news is that most people cannot tell you have a MI just by looking at you and interacting with you in a friendly, informal way. You may feel that you are different than everyone else, but no-one else knows.
People have such a huge variety in personality traits, anyway, that their peculiar little habits do not necessarily lead other people to jump to conclusions about whether you are unwell or not.
I remember a show that aired on SBS, where a group of professionals, including doctors, psychologists and psychiatrists had to observe a group of volunteers who all had diagnosed mental illnesses. The volunteers mixed in with a group of people who were perfectly healthy and they all performed activities together. The professionals had to try and pick out which volunteers had MI and also what their diagnosis might be.
They could not do it! The professionals had no luck what so ever in finding out who was mentally ill and who wasn't! So, if the professional don't know, how is anyone else going to find out?
The thing is this, you can form friendships and relationships with people and be very open and honest about what you like and dislike, what your interests are, what you believe in and value, etc, etc, and still not have to disclose that you have an illness. It does not make the friendship any less authentic.
Eventually, like, months or years down the track you may feel comfortable explaining that you suffer from an illness. Especially if your friend discloses something very personal to you and in doing so, shows that they trust you.
I have had very mixed experiences in telling people about my illness.
I felt I had to tell my husband before we got engaged, but it did not make any difference to him, fortunately. One of my friends said to me "You are very lucky he didn't run for the hills!" and I agree with her. I am lucky that I found a good man.
Another friend acted like she didn't really believe me or that I was exaggerating my illness. She just sort of said nothing and then changed the subject.
My family tried to pretend there was nothing really wrong with me and it was just 'business as usual'. No empathy; no understanding. They thought I had to 'snap out of it'.