Do you have health insurance? If so, I say go for it!!! Ride and fall off a few times if need be........ it is not the end of the world and it makes you stronger when you get back on.
I was tossed off the slowest dopiest horse ever the other day.... as soon as I knew I was going off, I relaxed and sumersaulted over his neck. I got back on, a bit nervous, but still confident..... I had my helmet on as always. It is not the end of the world to fall off.....
I adjusted my stirrups and made him do the same thing he did not want to do just before he threw me, and it was successful.
Riding does not always mean you will stay on. I understand your fear. We all have it. But just go with it. It really will be okay :)