Have I reached the dreaded 4 month sleep regression? Help! I'm desperate and exhausted!?

A little over a week ago, we started putting Our 19 week old in her crib from her Rock n Play. The first few days were rough but okay... and each night it's gotten worse and worse. Friday night she went to bed at 8:15 and was up at 10:50, 2:30 and 5:40 (which is unlike her; she usually slept 8:15-4, respectively). Last night she went down at 8:15, no problem, and literally woke up 10 minutes later and cried every 10-20 minutes until TWELVE THIRTY. She had a big bottle before bed so I know she wasn't hungry. Her diaper was clean. I held her, I rocked her, I "shushed" her... I even tried letting her cry for 5 minutes before going in there and each time she would fall asleep only to wake up shortly after and cry. Hubby and I slept in short shifts on the couch with her. If she was on one of us, she was fine. Obviously, this cannot happen like this. Have any of you been through this?? This is literally the worst night of sleep I've had since she was born. Is this sleep regression? And please tell me it is a short phase!