I am having the same problem! I just came here to post for some suggestions! My DD is 4 weeks and has so much trouble sleeping at night. Her trouble is she doesn't like sleeping on her back. During th day if I need to wake her, I just lay her flat somewhere and her eyes pop open. I do attempt to swadlle and put in bed for most naps, but with an 18 month old- it just doesn't happen sometimes.
At night she wakes for her nf, and then can't resettle. I've tried holding her to sleep, but as soon as I lay her down, her eyes pop back open. I've tried rolling her onto her belly, and then rolling her back onto her back after asleep, and have the same problem. I wait at least 20 min until she has fully fallen asleep. She takes a paci, but grunts and groans, and struggles against her swaddle when on her back. She spits the paci out, I put it back in for hours. Last night I was up from 1:30- 5:00. She would fall asleep and startle awake over and over. I finally nursed her in bed at 4:30, and she still didn't fall asleep after her feed. DS always ate at night, then fell right back to sleep. Naps were the issue with him. Sigh. I could try some white noise maybe? I'm exhausted!