No doubt it is because you have recently finished taking the Effexor. It is renowned for causing extreme withdrawal. It should ease up in a few weeks. Why were you taken off it? Was it causing intolerable side effects or was it not working? Maybe you could extend the taper, withdrawing from it very very slowly or try taking briefly taking Fluoxetine (Prozac), which has a less extreme withdrawal and doesn't usually require a long taper.
If you don't want to take any more antidepressants then you can still take action to reduce that extreme high level of fear. I would advise not drinking any alcohol, reduce caffeine to a minimum (no caffeine after midday), take time out from responsibilities if you can, rest as much as possible and spend time with good friends and family. I've felt that awful extreme fear myself. Like you are existing in your own personal horror film. It will get better with time and a bit of self care.
