I am new here, and I really hope someone will have advice that might save us.

My 7 month old baby girl has never slept longer than 3 hours since we brought her home from the hospital. Last night, for example, she was up crying 6 times between the hours of 9pm and 5am. She is the happiest, smiliest baby I have ever seen, so that makes it easier. However, Momma is slowly becoming depressed, and our marriage is really suffering.
The details:
She is BF, and we added solids twice a day a month ago at the doctor's request....she had dropped from the 40th percentile to the 25th.
Because of her sleep problems, we insisted on a paci, which she took at about 2 months.
She was in our bed exclusively until about a month ago, when we introdiced the crib. Now, she will fall asleep by herself in her crib @ 9pm.
She just will not STAY asleep.
I am not big on strict schedules (which might be part of the problem, I guess). But typically, she is up by 6, naps about 30 minutes at 9:30, naps again for about 30 minutes at 2, and then goes in her bed around 9 (after a big meal, making certain she is full). Then the fun begins.
She is up 5-6 times crying. I go in, pat her on the back, and give her the paci. She might sleep a few more hours, sometimes just an hour. I usually feed her around 2. Then she is up a few more times until finally we give up and bring her to our bed at 4:30-5.
Again, she is SO happy....even when she wakes up. I would feel worried about her being too tired if she were the slightest bit cranky, but she just isn't.
I know the paci is a problem. Is she waking to be "plugged" back up? It just doesn't make sense to me......I understand that she would want the paci when she wakes up, but why is she waking up SO often??
Any advice would really help, because I am dying here.