My baby, 6 months old

My baby 6 months old have been having purées for the last week, the last 3 days he keeps making swallowing noises every 3 min like he’s swallowing vomit/reflux back down, he has been coughing lots which we thought was a cold but then his nose was getting stuffy and I saw white formula coming through his nose, he is sitting up when he keeps making a swallowing noise. Can reflux randomly start happening at this age??? Or those symptoms do you know what it could be not sure it’s a cold anymore…