Colicky and not meeting skills

[Burned Out]

My son is now just about 7 months old and is still just always sad and always crying. I say he has resting sad face. If I leave a room for any length of time he screams bloody murder and cannot come back out of it. He spends his time crying if I am not actively holding him (can't sit with him, must boop boop boop) or giving him a bath (he loves baths). With his temperament being what it is, he has not been hitting his skill mile stones. We try practicing sitting up- he crys. We try practicing rolling over- he crys. We practice grabbing- he crys. He doesn't even really play either. We try putting him on his play mat to work on his skills and we all know the fit, red face, arched back, screaming, screaming and screaming. He cannot practice skills being held or in the bathtub and he is falling very far behind. My 7 month old basically has the skills of a 6 month old and I don't know how to help him. has anyone else had this problem with colic and skill development?