I think it is perfectly fine that you feel this way and I think that in time you may want another baby. I have a friend who has nearly 5 years between her girls because she just wasn't ready to have another one before then. It has barely been a year since you had Jazz and I am sure that there are many, many women that are not even close to thinking about more babies when their first baby is one.
There is still a few years before you are 30 (and that isn't even old these days to have babies!) so try not to have that pressuring you.
Someone once told me that it take a good 2 years to get over pg and birth (I don't know how factual that is!) and I'm inclined to believe it.
Try not to worry about it. Enjoy Jazz and maybe in a year or 2 you will know it is time for another one. It's ok to only want one child anyway.
HTH