What Causes Intermittent Pain In Breast Plate After Eating?

I am 28 years old and weigh 10stone 4.

I have a pain under my breast plate, just above my stomach.

This is the second day i have had it and it goes on and off. It is releived by peppermint tea. It hurts more after I eat and when I am lying down. Is it just heartburn?? I have never had it before. I have recently changed my diet lowering my carb and meat intake and have eaten much more of these things this weekend