Hi SB,
Great motivation and goal setting for yourself! Well done on getting to this point...you are goint to do well on this postive step.:)
First of all, have you gone through this link? it explains the anxiety = physical symptoms = more anxiety and symtpoms cycle really well.
Health Anxiety- The Super Scanner
http://www.get.gg/docs/SuperScanner.pdf
Once you understand that this is a normal part of the anxeity condition, it will be easier to accept that what you are experiencing won't harm you.
Then you can start out slowly, and if you become symptomatic, have the ability to push through.
Slowing down a bit if you are uncomfortable is okay...but do not stop. You need to go outside of your comfort zone a bit each time to make progress.
I had to do this because I am an athlete by trade, depend on my body...and couldn't afford to let anxiety stop me from being active.
You will learn to ignore your symptoms, monitor less...and eventually be free of the things that make you worried while exercising.:)
Best wishes, and keep us posted as to your progress!
S.C.