Please help my baby.

I'm literally desperate for help and some answers right now. My baby is 6 weeks old, backstory is..

She was born at 39 weeks via C-section. She has multiple heart defects (3 holes, right aortic arch, loose ventricular ring). Pretty much ever since she was born, she spends 90% of her time that she's awake, crying & screaming her little head off. We thought maybe gas, so started Probiotic Drops, Gas Drops, Gripe Water, doctor even prescribed Ranitidine, nothing helped. Thought it was the formula, changed it to a Gentlease, didn't work. Changed her to a Hypoallergenic, didn't do anything for her. She screams like I've never seen before. Her body gets SO stiff it's like she can't move, digs her nails into me, face red, hands turn blue, she starts choking & cant breathe and by the time she's done (lasts sometimes 2 to 3 hours) she's drenched in sweat. She is obviously in a ton of pain. All she does is sleep, eat & scream. I literally dread the moment she wakes up because I already know the hell that's about to be cast upon me. I've tried talking to the pediatrician twice already and I was basically blown off. Yesterday morning I finally took her to the ER after she cried all night, had a dry diaper for over 9 hours, and a 99.9 under the arm temp. She's also sounding really congested. She was admitted due to being dehydrated, but I need someone to tell me why my baby is in this much pain. I thought colic but my mom said my sisters & I had it as a baby and it wasn't nearly this bad. They took blood, urine & a nose swab for infections and viruses, which came up negative, but was else can they do? What do I ask for? What do I even say at this point? Her pediatrician has mentioned possible Pyloric Stenosis, but I don't think she projectile vomits often enough for that, although she has multiple times in the last week and she also spits up a lot. Any nurse or doctor on here, even a mom who went thought something similar.. help! 😭💔