7 month old, diarrhea, wakes up screaming (long)?

My daughter will be 7 months on Sunday. For the past two weeks she hasn't been herself. It started out with her being very irritable during the day at daycare - but when I picked her up in the evening, she was fine with me. Then she started having diarrhea - up to 3-4 times a day. She was staying hydrated and still eating well, so I chalked it up to a stomach bug that was going around her cl. Then last monday, her eating habits began to change - she was still drinking her milk, but only 2-3 oz at a time and was refusing solids - even her favorites. At that point, i took her to the dr. who thought that she had probably contracted the stomach bug - he gave me a special regimen of pedialyte and special formula, plus Bacid tablets to help with the diarrhea and cramping. That night she had a fever (the first since this started). the fever continued off and on for two days, but was low grade (101.5) and responded to tylenol. She's been fever free since friday - Sat and Sun her stools started to get firmer. Saturday night, however, she woke up from a dead sleep screaming bloody murder. She was inconsolable for about 30 minutes, then finally fell back to sleep. Sunday afternoon, she had the same type of screaming fit and finally screamed herself to sleep; same thing Sunday night. I'd given her tylenol and mylicon - not sure if i was dealing with gas or teething or something else. Then yesterday (Monday) at daycare, they advised that she was cranky all day as usual and had another 2 diarrhea diapers, and woke up from her nap screaming. I have called the pediatrician again, but I'm wondering if anyone else has had any similar symptoms like this with their children. I'm trying to think of all the possibilities - virus, gastrointestinal problem, gas, teething, simple separation anxiety (she's very attached to me). I'm just at a loss and i hate to hear my little girl screaming in what sounds like pain.