Congested baby

So my son will be 7 weeks tomorrow. Since he was born he’s been very congested. A few weeks ago we took him to urgent care because the congestion was causing him to wake up due to coughing and chocking. The doctor said he was fine his lungs were clear and she recommended saline drops a humidifier and a nose Frida. For awhile it all has been working. But lately it’s been acting up again. Nothing seems to help. It’s only really at night when he’s sleep on his back. Any suggestions???? I’m up all night just listening to him breathe to make sure he’s ok. 😩