Vomiting at Night

My daughter, who is 11 months old, has been vomiting once every night since last Saturday. She's had a cold for about 3 weeks so we are thinking that maybe it has to do with mucus that she's swallowing, but we don't know why it wouldn't have bothered her the first two weeks. She is always able to drink her bottle afterward, but has trouble going back to sleep easily. Normally, she sleeps 12 hours without us hearing a peep out of her, so this is troubling (and exhausting). She usually eats a lot of solid foods at breakfast, lunch and dinner as well, but the last few days, she's been gagging and coughing a lot during her meals, and so she's not eating much solid food. She also usually drinks about 4-6 oz. per bottle several times a day and this last week she's only been drinking 2-3 oz. at a time, with an occasional 4 oz. one. I'm worried that she maybe has swallowed something she shouldn't have and it is causing her to cough and gag. What I don't get is why she's only throwing up at night, not during nap time (which she's still doing fine). She was also diagnosed with an ear infection last Monday, which she's been taking antibiotics for. We didn't start her on them until Thursday because it wasn't until then that we were convinced she didn't have some sort of stomach bug. So, anyway, I'm just really worried about her and wondering what kinds of ideas or experiences anyone else has had with something similar. Thanks for your thoughts.