What Causes A Foul Odour From My Vagina?

I have an odor that comes from my vagina. I must be honest. I have not been to a gynecologist in over 20 years for sure. I am a clean person. I do not see any discharge. I have gained so much weight though that I find I have difficulty wiping myself. I know about proper wiping and practice these methods religiously. Actually when wiping myself after a BM I have to contort my body when reaching behind and sometimes I get muscle spasms. Anyway it is becoming annoying to me. If I can smell the odor, I am afraid others can as well. What can I do to help besides going to a physician. There is no itching. It is embarrassing.