Sleep regression?

My daughter has been going to sleep with her routine for months. Sometimes a little fighting, but nothing too bad. The last 4 nights she’s fighting it so hard. We go through the bedtime routine, she’s fine all the way through. Until I turn off the lights and she’s completely loses it and won’t calm down. I hold her, rock her, sing to her, rub her back, tell her everything is ok. She just screams in my arms and won’t stop. Last night she screamed for two hours. Is anyone else going through this? She’s not sick, she is only behaving this way at bedtime.