15 month old with a lot of flem throwing up alot. What to do?

My 15 month has had flem/coughing issue for about 3 months now. She gets so much junk in her throat that she throws up a lot. She got tubes in 3 weeks to help with chronic ear infections. Her doctor says the throwing up is just from allergies and cant take anything tell 2. I am just really worried and want to get better! Does anyone have similar experience if so what helped or does anyone have idea what to do. I am going to call doctor again. She is also on Cough syrup right now which is not helping