What Causes Coughing Up Of Mucus After Consuming Food And Water?

My husband is sixty three. He has a problem of eating and drinking. He can swallow fine. But after fifteen minutes he starts coughing up this clear mucus for hours. If it doesn t come up then he has a hard time breathing. He hasn t had any real food for a week now he s lost around thirtylbs . If he walks or stAnds he starts coughing and breathing is raspy. I ve tried hello puddings nothing works. We have been to the emergency three times now scopes have been done they c a by find the problem and act like it s no big deal and send him home. They gave him some anti acid med but he can t take it. He starts coughing so bad. I feel like I m losing my husband and at my last straw we have probably spent 6000 and no one knows what s w err ing how long can a person not eat