My baby stopped sleeping through the night?

My daughter has slept through the night since she was 6 weeks old with no problems. When she was 3 months old she started to wake up numerous times (almost every hour for 5 minutes) crying/whimpering but when she was in a semi sitting position (car seat) she slept straight through for 9-10 hours. We started her on acid reflux medicine when she was 3 1/2 months old but she is still doing it. As soon as I walk in her room and put the pacifier in her mouth or turn on her mobile she stops but then wakes up again in few hours and I do the same thing. I've tried just letting her cry but after 10 minutes I go in there. She's not hungry, cold or hot and half the time her eyes are closed and she is just 'whining.' Is this normal for a 4 month old?