Sick 3 month old-help!!!

When should I bring my son back to the doctor for congestion? He sounds awful, coughing, and loud stuffy breathing. Snoring, trouble eating, overall bad feeling. He’s had this for a little over 3 weeks. We have been using nose drops and sucking everything out but it’s not helping long term (more than 5-10 minutes). I’m so close to just taking him to the hospital because I feel like his doctor isn’t helping us. I’ve applied for different doctors but most are booked for weeks or not accepting new patients