My 3 year of male Frenchie has recently developed a quiet cough that sometimes ends with him trying to gag something up (rarely does anything actually come up). The vet took x-rays and blood work and found no clear cause. Put him on an antibiotic (Doxycycline) which cleared up the cough/gag within 2 days. The problem is it came back a few weeks later, and this cycle has continued to happen every couple weeks for the past 2 months. Has anyone experienced this before or know what could be causing it? Luckily the antibiotic has cleared it up each time, but not permanently. Thanks!!