Hi W., my daughter, who just turned 2, had similar problems. When she was nearly 3 months old, she developed RSV, and she used Xopenex to help her breath. The first year of her sweet life she would suffer from the same symtoms you described (cold, cough, difficulty breathing and wheezing) in a pattern. She would get sick, be sick with the systems for about 10-14 days (gradually getting worse and then better), and then she would be fine for 2-3 weeks. After that, we'd start the cycle over again. It was rough, but after she was old enough to take IB, then that helped her sleep during her coughing boughts (nap and at night). I often would sleep sitting up in bed or rocking chair holding her or next to her in bed with her propped up on pillows, so she and I could get some sleep.
The good news is that she has thrived in every way, and she now goes longer stretches between the boughts of colds. I now only give her Xopenex a couple days during the worse of her colds, and I give it to her only before nap and at night. It seems to help relax the coughing reflex enough for her to go to sleep, and I think the IB helps.
My pediatrician explained that babies can't get rid of the mucus fast enough so they cough, wheeze and have difficulty breathing, especially babies who have had RSV. My pediatrician said that as they get older and their bodies grow then they will be better able to cop with the mucus. I have found that to be true with mine. It's tough going through these constant colds and sleepless nights, but as your baby girl grows, she'll get stronger. She just needs a little help from you during those days and nights when she's at her worse during a cold. Hang in there!