Hi H.,
For the first 3 weeks we had trouble with this too. Our pediatrician shared with us how she had to sleep in her recliner for the first MONTH with her son before he would sleep in his crib. So, what you are experiencing is normal.
I chose not to co-sleep. It may be right for you and your family, but it was not something I wanted to do. I felt that I would only have to break that habit when my son got older because I knew there would be a time when I wanted to get sleep of my own. I did not want to have to go through weeks of forcing my child to sleep in his own room - imagine how that might feel like punishment - "why can't I sleep with mommy anymore? what did I do wrong?". At the same rate, MANY parents successfully co-sleep and have WONDERFUL results, so do what feels best for you.
For our son, we let him sleep in his room strapped into his vibrating bouncy seat from week 3 til week 8. Sometimes we had to rock him for 15-30 minutes before putting him down, but once we got him down he was good til the next feeding. At week 8, we switched him over to his crib and he had no problem transitioning. We also swaddled him with a SwaddleMe blanket. Our bedtime routine was the exact same thing every night, and we turned on our white noise (ocean waves) before leaving the room).
Around week 8 he started dropping the middle of the night feeding and started sleeping from 10:00 pm until 6:30 am. Now, at 4 months he goes to bed at 8:00 - 8:30 and wakes up around 6:30 - 7:30. I don't know about you, but that sounds like FANTASTIC sleep to me!
Good luck to you - I know how vitally important sleep is!