Hi ,
sometimes rashes on the stomach can be metal allergies from buttons or belts. A mild steroid ointment may help this clear up , with your GP's advice. It could really be a number of reasons ranging from stress to hormones and allergies. The best thing to do if you are concerned and it doesn't clear up is to ask your GP for a referral to a dermatologist. This will put your mind at rest and give you an expert diagnosis and appropriate treatment. Try not to worry, and you may find that doing something positive about getting a clear indication of what it is will make you feel better. If you cannot wait , then going privately could be an option if you can afford it. Unfortunately as we get older all number of things tend to go a bit haywire !!
Good luck.
Pepperminty xx