Immune defiency in 11 month old baby! HELP! pls

Hi, I joined this discussion group in hope that someone can help me out. My son has been sick since he was 4 months old. It all started with a cold, I have two other kids 6 year old and 2 year old perfectly healthy. They all got sick at the same time but the baby never seem to get better. It was nonstop mucus to the point I had to do nasal irrigation everyday sometimes multiple times. The first time I took him to the dr. He was prescribed augmentum antibiotic. Still on the antibiotic he kept having alot of mucus secretion though it had change colors, from yellow, greenish to clear. I communicated this to his pediatrician and he advice to finish the antibiotic treatment. The minute he was done he began to have the same mucus and fevers. i changed three pediatrician at this point he had been already on 4 different antibiotics and none worked. I finally got a dr. To listen and sent me to an ENT which immediately stated he had chronic sinus infection he needed his adenoids removed and clean him up. He actually grew a lump on the parotid gland ( a lymph node got swollen). She than changed him to another antibiotic, by the fifth day on the antibiotic he started having high fevers and was just miserable but I was out of the area. I reached out to the ENT she recommended to see another ENT where I was. This ENT saw my baby and immediately addressed a concern on his enlarged lymph nodes. He did say he had a chronic sinus infection but he was more concern about the lymph nodes. I left there with another antibiotic and his recommendation that he needed surgery immediately because he was extremely congested. I head back and surgery was perform he had his adenoids removed, and put some tubes in his ears ( at that point he had bad ear infection). They took cultures of his sinus which stated he had H influenza, adenovirus, pseudonomas and endovirus. Once the surgery was done we head home two days later he was left in observation. Once home the lump started to grow dramatically. I head back to the EnT they perform a ct scan and he gets hospitalize again to get antibiotics thru the IV. Infectious disease gets involve and they discover that the antibiotic he was in was not covering the pseudonomas so we left home with another antibiotic (levoquin) 8th antibiotic at this point. 2 weeks later he creates an abscess, back to the surgery room to drain it and get a biopsy. Immunology gets involve and they start making test at first one of the test stated he had very low DHR which lead them to believe he had CGD. They did a repeat and the numbers came normal. PCR came negative for atypical mycobacterium but Infectious disease swears he has a mycobacteria so he was put on azithromycin and rafampin. This has been three months he has been on those antibiotics and he still has inflammation and swelling. Immunology continues their work up and find that he might have a bcell disorder. It stated that his transitional b cells are enlarged and his memory b cell are very small amount. But with even these results they decide not to proceed with anything since he is very young in age plus he was looking stable. Now he has another sinus infection and ear infection. ENT performed an MRI and confirmed he has severe edema so refuse to go in and remove the infected lymph node. At this point nothing has grown on the cultures , we cant confirm he has an atypical mycobacteria. When they did biopsy the lymph node pathology found necrosis and granulatomous. And that is the only thing that leads to believe it is a mycobacteria. But besides the mycobacteria he keeps getting these infections and bacteria and though immunology had those results from the b cells they believe he might not have an underlying issue or maybe it was just "bad luck". I see him getting sicker by the minute even under those antibiotics. I have to do the nasal irrigation twice a day and its chunk and chunks of mucus.
Something is not right and I would hate to see him get chronically sick as he was with the sinus just because we are waiting to see if he "grows out of it". What I do know is all these recurrent infections are not normal and my two other kids are perfectly healthy. I need someone to help me before its too late. And if there is someone that has been thru this I greatly appreciate any advice, reference, referrals anything!