My son is just like that. He had been since 6 months whenever he got RSV. We would normally have about 6 or 7 chest xrays a year. I even went as far as to seeing a pulmonologist. He was having to use pulmicort daily and albuterol as needed. I hated it for him. For one, he hated the treatments. No matter how cute of a machine I bought or let his stuffed animals do it with him... heck I would even do them, but I have asthma and am supposed to use symbicort so it didn't really do anything to me... I would have to practically hold him down.
Mine turned 4 in June of this year. We had adenoids & tonsils out/tubes put in last year in Oct. I think we only had to do one breathing treatment last winter (it's always worse in the winter). Plus I have only had to do 1 round from January until now, with zero chest X rays for the year. We have done away with the pulmicort and everything else. Come to find out he doesn't have real asthma, as in he doesn't suddenly have attacks. It's only whenever he has a cold or allergies.
Have you had your child tested for allergies? Mine is actually allergic to mold spores, higher concentrations of mold are much worse. Normally I would not notice the initial allergy because it wasn't typical, he wasn't around cats or dogs and he didn't really eat many new foods. I live in Louisiana and there are mold spores all in the air on any given day. It wasn't until he would develop a respiratory infection that I would notice something was wrong.
Once he was tested and we learned how to control it and prevent... as much as possible with this being LA... he rarely gets sick anymore. I think they also, somewhat, grow out of it and develop better immune systems. Plus I have learned to spray down the outside of my house more frequently, or not purchase bath toys that can suck water into them. Simple little things like that have drastically changed the respiratory infections since he doesn't have the initial reaction, it doesn't further develop into something much nastier.
Mine is prescribed so many meds it's ridiculous. Pulmicort, albuterol, singulaire... on and on. I do not give any of them to him anymore.
I was also advised NOT to use a warm humidifier at all. They do seriously spread germs and bacteria. There really isn't an effective way to keep them clean. Plus, if you can't breathe, I know from experience, the LAST think you want is warm moisture anywhere near you. It makes it harder to breathe. A cool mist one is much better but still just as germy.
I found these little vicks warmers walgreens. It plugs into the wall and you change out the cartridge. They are dry or kinda gooey like (I don't know if thats a word, but w/e). They aren't hot if you touch them, either. The warmer heats the vicks on the pad and thats all that is emitted into the room. No warm moist and germs flying everywhere and no heat to burn him with.
Try having the allergies checked. I never would have thought that about mine. If you ever need anything, you can message me. I'm sorry your little guy is going through this.