Sounds normal to me. Cat heats can be pretty unpredictable.
You need to have her spayed ASAP because the more times she goes into heat the better her chances are of dying from a pyometra, breast cancer or other HORRIBLE reproductive diseases. I've seen many cats die or become severely ill first hand. It's not pretty.
My cat is smarter than your honor student.
Stop Dog Fighting ~ Neuter Mike Vick!
~ RIP Timmy ~ May 2009 - November 6th 2009