Jerseys fit longer than regular shirts, so they cover your back all the way when you are bent over on your road bike. But if it's really too long, the pockets hang too low and that's no good. When you're in the biking position, it should cover to about the top of your crack, not much higher, and definitely not so long that you sit on it.

Keep trying stuff on until you find something that you like and fits. If you don't have good local bike shops, order a bunch of jerseys (Excelsports, Colorado Cyclist, cbike, Competive Cyclist, departmentofgoods.com....) and return the stuff you don't want.

PB brand is kind of the low-end of bike clothes, they often fit funny and look bad. And they don't carry the nice euro-fit high end stuff. Primal or Pearl Izumi would be another step up (from PB or REI), then Garneau, Castelli, Capo, Campagnolo, Assos, Rapha.

Jerseys should be more fitted than regular clothes, you don't want them flapping in the wind and sagging. You only need one or two jerseys to start with (don't ask me how many I have, it's embarrassing), so be willing to spend a bit on them. Don't put them in the drier (washer on cold is ok) and they will last a long time.