If you have an old musty. moldy house then a humidifier is the last thing you need! It will just help the mold grow. I can relate to your story, I had always had allergies but they didn't get out of control until I moved to South Carolina. And my house was old and musty, and I felt worse at home until we got some HEPA filters.
Honestly, It wasn't just one thing that helped me. It's been a combination of drugs, allergy shots, sinus surgery, HEPA air cleaners, daily sinus irrigations and moving from humid SC to the desert of Arizona. And even now, I'm not completely well yet, but it is under control, and I can function like a human being again.