I need help. 3 month old will not sleep

I have been battling sleep issues since day 1. Please tell me why it takes 2+ hours for my baby to fall asleep. Bath then Nursing for 1 to 1 1/2 hours. Falls asleep. Go to lay her down and immediately she's awake. Grunting, arching her back and an ungodly screaming crying. She's fed, dry, swaddled (we've tried unswaddling), takes medicine for acid reflux, crib is angled. I know she's still little but I'm so friercly jealous reading about how women are bathing their LOs and 30 minutes later they're in bed fast asleep and sleeps through the night.  I just need to understand what my LO needs so I can do it. Being held isn't it either because I'd gladly hold her to sleep but she cries and arches her back. I'm so stressed out!!!! JUST GO TO SLEEP!!!!!