Whether or not you feel comfortable is the main consideration for choosing a frame size.
Also, I don't recommend you pay much attention to the seat-tube length (which seems to be the standard way of measuring frame size) because
Headtube length is more significant because changing the seat-to-handlebars distance is more complicated than changing the seat-to-pedals distance.
If you don't have any pain problems while riding now, changing frame size/shape might just cause them.