Donna,
I didn't start standing up on hills until I'd been riding over 2 months most every day. At first, I coould not balance at all when standing...scary! Don't expect to be able to do everything before you get a bit more experience. There's nothing "wrong" with you- you just need more time to build up your skills (just like I do as well).
I practiced on a SMALL hill, and partway up I would put my hands on the hoods and pull myself to stand- I would just stand for one downstroke on each foot, wobble along, then had to sit again. With practice, I could stand for several strokes, and now it's just plain FUN to stand and power my way up a short hill....when I *can*. Long hard hills now...that's a real challenge and I usually spin them in low gear, envision clouds, and keep my breathing deep and even.

P.S. I just love your avatar picture