Well I'm glad you were finally able to get one! Great set up you've got there.

Nah, it's not because the bow is new, but it is because YOU'RE new to it. You're using muscles you haven't used before, but you'll build up to it quickly. Back that rascal off as much as you can (if it's a 30-40# bow, you should be able to get it down to around 27 or 8 ) and shoot it there for a while. Steadily build up to where you want to be. You'll be surprised at how quickly that happens.