I had the same experience. Couldn't breath through my nose, I could only sleep on one side at night or I couldn't breath. I also had to use nose spray all the time. I also had an allergy test done that showed only very mild allergies, nothing to warrant the reactions I was getting. Turns out that I had a deviated septum. I diagnosed it myself after my (ex) pcp had looked up my nose a million times and hadn't said a thing. I made an appt with an ENT and he confirmed what I had suspected. I had surgery to correct it and have had no problems since. Also, if antihistamines make you sleepy and are not giving you relief, try a steroid nose spray like flonase (Fluticasone) or rhinocort (budesonide) Before I had surgery, the rhinocort and netti pot type thing made breathing much easier.