My 10 month vomits phlegm when she lays down to sleep. going on 4 months, about to go insane. whats wrong?

she has been sick off and on for 4 months. ear infections, allergies, etc. every time this happens she gets drainage, which leads to vomiting phlegm. she starts out as soon as we lay her down, vomiting every 5-10 minutes and then it spaces out but continues throughout the night. we have been to the dr atleast 9 times, but they say its just drainage and then say to give her zyrtec/benadryl. i am so stressed and at my wits end! has anyone gone through this??? is there something more serious that i should be considering?? i am desperate and want some answers!