I can feel your struggle and pain in your message. I am so sorry this is happening. I agree with all of the great points from dfb. Looking at your food, water, vitamins, exercise. Keys to getting our overall minds in the right place.
In the short term, it sounds like you need a plan before your next psychiatrist appointment. Does your current doctor ( the one who prescribed the prozac to replace the Effexor) have an electronic chart that you could send a message? It sounds like you have come off of the large dose of Effexor and the symptoms you are having may not necessarily be withdrawal effects from Effexor but simply that you are not taking anything at a substantial enough dosage to manage the anxiety. When did the doctor prescribe the prozac and have you been taking it?
I have a long history with anti-depressants and have immense empathy for where you are at. One other note, have they prescribed you any type of anxiety medication? Ativan?
In good health,
SF