PLEASE READ!!!

my baby boy is three weeks old and has recently started crying intensely. it was on and off (day wise) before but has become a daily thing now for the past few days. it gets worse in the evening and at night. it’s high pitched, very intense and loud. he does it for hours with off intervals of a few minutes. they sound like he’s in pain, he cries until he is purple. i brought it up to the doctor but she thinks he’s fine. normal baby things. she said could just be a little gas but it’s so bad that i’m worried it could be more. possibly colic? maybe something else? any ideas? i hate seeing my baby like this