Yep, it could be related to depression. How to deal with it works out to be an individual experience for everyone. I think what you are trying to say when you say
I just feel estranged from myself and can't seem to get in touch with me again is you can't find what is important in your life right now.
One thing that you need to do is focus and look for the things that you are doing well. Learn to acknowledge even the small occasions when what you said made sense to someone. (Like now) congratulate yourself for finding your way to your classrooms, because your memory does serve you.
Your main focus seems to be that you are not expressing yourself as clearly or concisely as you like. Some sort of anxiety has gotten a hold of you in this area. One thing is for sure you are not alone. The fear of public speaking (expressing oneself to another) is one of the greatest fears in society. Use the Anxiety Free tape if you have it. You seem to be beating yourself up for a false self limiting belief. From what you posted I believe you expressed yourself well. So you seem to be focusing on your weakness rather than your strenght. Yes depression is one of the reason you could be doing that and it creates the downward spiral. You need to deliberately remember to focus on your strenghts that is the only way you can empower yourself.
If you want to work on expressing yourself with a more relaxed ease, and if you have the New Behaviour Generator (that would be the one to use). Try the following.
Can you think of anyone, a friend (even a teacher) that you admire for the way they express themselves that you would like to copy? I mean just their ability to express themselves. While for you right now it seems a frustrating effort to express yourself because your mind seems to be blank?, being able to express yourself is just a habit.
It's when you set your own goals for yourself that paraliminals work best. Remember to think of the goal you have whenever you use a paraliminal.
Alex