sleeping!!!

How in the world are you all getting your babes to sleep 3,4,5 hour stretches??? My baby girl will only go 2 tops. I am exclusively BF and even the one time my hubby gave her a bottle she still didn't sleep any longer than 2 hours. She is 4 weeks. We cosleep and this week I have started putting her in the little snuggle me on the bed next to me. She will only sleep there for a little bit but then has to be next to me all night.