In tears..

So I am calling the pediatrician tomorrow morning but right now I'm just crying and worried about my baby boy (18mo). Just ranting a little bit. He came home last weekend from his dad's with a cough amongst other things physically. It didn't sound too bad and it was a dry cough but I noticed that the cough medicine and Vics weren't working/helping with it. So obviously I was a little worried but he didn't have a fever and no other symptoms other than not really eating meals just snacking, I was just glad that he was eating at all. I told his father this weekend that he was sick and to let me know if any other symptoms popped up or if he got worse. I texted on Saturday to check in on our son. He said that of course he was fine and that his cough was doing better but he had coughed himself awake Friday night. I got a picture of him and he looked soooo tired. His eyes were visibly red and according to his dad he had just woken up from a nap so I had no choice but to take his word for it. Son comes home today and his dad tells me that he was giving him Motrin to help him with his cough. Yeah a fever and pain reliever, not cough medicine, for his cough. I just said okay and took our son and went back in the house because saying anything wasn't going to get anywhere and it's not the first time he's done stuff like this and not seen an issue with it and it really just wasn't worth my time knowing he won't listen either way. His cough is now worse than it was before. It now sounds wet and he's having coughing fits to the point his face turns red and having a hard time stopping for air. I am beyond angry at his dad. I am mad at myself because I can't do anything when he goes over for the weekend. I am so worried about my baby and I wish I could take all his symptoms away. I am so scared he has something serious because medicine isn't working and it's getting worse. Thankful there are still no other symptoms. On top of that he has another rash forming on his bum as usual from when he comes home from his dad's and also has a little red bump next to his genitalia (assuming bug bite). I feel so bad for him and like I fail him because he has to go over to his dad's who doesn't even take care of him when he's there....he's literally on games the entire time and I constantly worry about son's wellbeing when he's there

Hoping to get my little boy into the doctor's tomorrow and I don't think I'll ever stop beating myself up for not taking him in before the weekend..