Going insane with 4 month old

Hi everyone I have a 4 month old boy, from the start he has been a very intense baby. Dont want to go on forever with back story but he has been to the doctor sooo many times to address fussiness, has had multiple tests with no clear answer other than GERD which he is on medication for.

Anyways I’m going insane with the constant screaming and crying. We had 2 good weeks right before he turned 4 months old, only crying when he needed something, smiley all day. Now we’re back to square one. Constant crying. Screaming like he’s being torn apart. I live in an apartment and I’m so worried someone will think he’s being neglected but i just cant seem to keep him happy. The longer it goes on the more i lose my patience and i feel myself just wanting to scream but I don’t. I know there isn’t much to do or say to fix it but just need somewhere to vent and see if anyone else is going through this.