Remember that this IS his job. A psychiatrist is a medical doctor, and any medical doctor is hired with the purpose of figuring out whatever ails us and helping us come up with a plan to deal with those ails. Can you think of it that way?

For instance, if a person had really ugly rash in some private area of his or her body, that person might go to a doctor who would have to look at that in order to see what was going on, try to figure out what is going on, and hopefully come up with a way to help relieve that rash. Getting undressed and having another person, that doctor, look at that rash might be really uncomfortable, even perhaps feel embarrassing, but to the doctor, that is pretty normal, day-to-day business. That's his/her job.

Additionally, sometimes we go into a doctor certain we already know what's wrong with us (X), but once the doctor starts investigating, they use their knowledge and explain to us that, no, what's actually going on is Y. That's not ego; that's a more particular, more trained, set of eyes. A few years ago I woke up in horrible pain, and it was on my lower right side; I was pretty certain it was appendicitis. I went to the ER, and once the doctor did some investigating (ultrasound/x-rays/blood work), he diagnosed a kidney stone. He explained the symptoms such as mine were presenting were very similar to each other,but it was definitely not appendicitis.

I just encourage you to do what you and your doctor discussed: focus on the treatment of your symptoms rather than use your disagreement with the diagnosis (which probably won't make much difference in treatment in the long-run) and your discomfort with opening up to him (probably a common fear and discomfort for many people in this situation) as a reason to reject help by running away. Allow someone to actually try to help you. It doesn't all have to happen at once. That's okay.

As far as a blog goes, you don't need to find an app. Buy a notebook. Start writing. There is something to be said for the tactile action of writing by hand rather than punching keyboard keys. You can draw. You can doodle. You can't delete things permanently, losing them. You can paste pictures or articles into the journal, etc. My therapist always said the messier, the better, when it came to journalling. We tend to edit ourselves a great deal on a screen, and we tend to lean to our perfectionist tendencies rather than being spontaneous and authentic. Don't let not finding an app stop you from starting. Paper and pen is easily at hand.

Best of luck to you.