It is possible, though much less common, to develop a food allergy later in life. Though your reaction does not seem at first to be an allergic reaction, the fact that it is occurring when you eat peanuts (a very common food that people are allergic to), your doctor(s) should take this reaction seriously.
Most of the time when people develop a food allergy, they get certain characteristic symptoms. For example a mild allergic reaction would be the development of hives
, itchiness, severe abdominal pain
or nausea all shortly after the ingestion of the food. In severe cases, the culprit food will cause swelling in the airways making it more difficult to breath and even sometimes a low blood pressure. In these cases, the food must be avoided at all costs and the effected person carry a rescue epinephrine syringe to inject themselves if need be.
The only way to find out if this is an allergy is for you to be tested. I suggest that you schedule an appointment with an allergy specialist. An allergist has the resources to perform a special type of allergy testing to see if your immune system reacts to peanuts. If it does, then your symptoms may be due to an allergy.