Re: Mercury square Midheaven - problems communicating (especially in public)?
I don't think the issue is Mercury square MC on its lonesome, so much as Mercury conjunct Neptune, with the square to the MC thrown in for good measure. Neptune tends to "dissolve" what it touches. In your case, your thoughts and communication may find themselves swept out to sea by Neptune's tides!
The positive side of Neptune conjunct Mercury (along with your moon-Jupiter) is that you probably have a rich imagination and inner life.
I taught students for many years, and have a mild dissociative disorder. I found I needed to speak from an outline or notes. It wasn't that I didn't know my material, but just that I could so easily lose my train of thought. See if you can arrange for some kind of memory aid to get you through public speaking. Power point presentations (or even old-fashioned overhead transparencies or printed hand-outs) are great because (a) you can follow them, and (b) if you do get a bit confused in mid-sentence, your audience has a visual aid to help them get your points.
"That which you have tried yourself, which you have experienced, which you have recognized as true, and which will be beneficial to you and to others; believe that, and shape your conduct to it." --Buddha, Kalama Sutta
"My friends, love is better than anger. Hope is better than fear. Optimism is better than despair. So let us be loving, hopeful and optimistic. And we’ll change the world." --Jack Layton, Canadian NDP leader, "Letter to Canadians," written two days before his death from cancer.