Thanks everyone - all the advice is greatly appreciated.
I think I'll give RPM a miss, even though I miss it, I'm too scared I might do some harm.
I'm reluctant to tell my instructors just yet as my inlaws and several friends go to the same gym as me and I don't want them to find out yet! I'll feel a lot more confident that I'm doing the right thing once I can let them know.
Thanks again!