I Have A 6 Month Old That Is Always Fussy

I have a 6 month old that is always fussy and kicking a lot and always having a tantrum . we had her seen at her drs and also put her on new formula which is not working and she is always crying . we think she may have a issue with her stomach but dr wont listen to us she screams at the top of her lungs all the time like shes in pain . she does have colic . but we think there is more going on with her.