What Causes Intermittent Twinges Of Pain In Upper Chest?

I have had intermittent little twinges of chest pain in left upper chest. Sonetimes I will have them several times a day and then can go for days or weeks and have none. These are not exertional. I am a 46-year-old female, 5 4 119 pounds. I have always had anxiety so just assume this is what it is. But most of the time the twinges of pain occur I am relaxed.