Baby cough. What to do?

My 7 month old son has developed a cough. It started about 3-4 days ago. I took him to the doctors Wednesday because he had a little temp of 100. They checked him over and said everything seems to be okay, and that it’s just a viral sickness that’s going around.

Now that a couple days have passed, he has no fever but his cough is still there and I’m beginning to think it sounds a bit more rough. It’s only extremely tough during the night when he laying down. During the day he’s not bad at all. At night when he’s sleeping, I feel like he’s almost gasping for some air after he has his coughing spells.(which last about 5-10 secs).

Any suggestions on what to do?? Should I take him back in??