dog can't stop sneezing

I nee some medical advice concerning dog. I have a 10 year old beagel, and the problem is she is sneezing all the time and when she sneezes mucus comes out. Plus she also has what they a backward sneeze. It almost sounds like when we have a cold and and have that film stuck in your throat and you are trying to clear it. First I was told it might be allergies and to give her benadril. but nothing seem to help, I'm trying just about everything before taking her to a vet. Because I'm on a tied budget and vet's can get very expensive. So before I go that
route, maybe some one could give me any ideas as to help her. She's not in any pain or anything like that, aside from being a little overweight and the sneezing she's fine. If you can give any help or any suggestions on medications. I would appreciate it greatly.