How to stop co-sleeping with newborn

For the past couple of days my three week old has been cluster feeding and after feeding she stays up for about an hour and during this time I can’t put her down without her crying. When she does go to sleep I have to hold her for another 30-40 minutes so she can be in a deep sleep before putting her down, or she’ll wake up and scream but she wakes up every 2 hours to eat. I’m exhausted and i find myself waking up with her still in my arms. It scares the crap out of me because if I’m so out of it that I don’t even remember picking her up or going to sleep, i shouldn’t be holding her. Anyone else have this problem or can give me tips?

*my SO goes to work at 3am and helps out a lot with feeding her and what not but after he leaves I’m on my own so I can’t have him wake me up or anything.