When did your symptoms start? Was is suddenly after eating something spicy or did this happen gradually?
Is this discomfort almost in the center of your chest (between your breasts)? Are you feeling any reflux (heartburn)?
What do you normally take for reflux? Have you missed taking any medication or eaten something that is acidic, spicey, eaten then laid down < 2 hrs. after eating, had caffeine or alcohol, etc. -- the things that set off reflux?
Is the Pepto helping you? Too much of it is not good as it contains aspirin- like properties and can eventually worsen your problem.
I would see your doctor who prescribes your reflux medication and talk to him/her and in the meantime avoid the things I mentioned above to avoid reflux. Should your symptoms worse prior to then or you start to vomit blood, go to the nearest ER.
You should check your other breast as well as it may be the same.
I feel that the pain you are experiencing is to do with the stomach which is in that area. You are eating something that appears not to agree with your stomach.
Keep off all fried foods, junk foods, highly spiced and processed foods as well as cakes, biscuits and fatty foods. You may also find that eating bread and bread products may worsen your condition. Keep a written record of what you eat and drink to see if it worsens your condition.
You should be fine with most vegetables and fruit. Boil or steam your foods instead of frying.
East small amounts of food rather than one large meal. It is better to eat smaller quantities and to spread it out during the day.
Best not to eat for a few hours before bedtime.
Camomile, peppermint and dill may help ease your stomach problem rather than relying on Pepto-Bismol. Take your acid reflux medication as prescribed by your doctor. If you feel this is not working, make an appointment to see your doctor as you may need a different acid reflux medication.
Probably should see your gyn or GP, have them check it or have a mammogram, also, a GI series would not hurt either.