Ok K., I'm a K. too. I have b&g twins and my son slept with us until 15months of age. But we also didn't mind it until he grew.
(I wrote all this thinking your son was 6Months. 6 weeks is easier- no pillows though, instead use swadling blankets.)
Try: (The baby should sleep in another room)
1. falling asleep with your son in his room a floor a futon matress works well.
2. Sleep with his blankets, pillows, animal, whatever you are keeping in his crib.
3. do the above for 3 nights, then on the fourth night start moving him into his own crib. When he wakes up, consistently pick him up and rock him til he stops or bring him back to bed and put him back in his crib for as long as it takes. this can happen over and over again all night long. Stay up all night long and do not change the next day's routine. On your fifth night you will have won the battle because he will be too tired to fight and so will you.
4. bed training will still continue- consistently be there for him. but be consistent on bed time, that he is in his room, that he sleeps in his crib, but you can snuggle and pick him up if he fusses but you have to stay in his room after bed time.
5. At 15 months I figured out that if i just listened to soft music and rocked him that eventually he just got that he wasn't leaving and willing went to bed.
On Subsequent Nights: I suggest a bedtime routine, for us,
its bath, playtime, book or bottle, brush teeth, soft music, bed time (9:00pm). It is okay for them to cry for a while as long as they are not sucking air and becoming hysterical it also wears them out. Stand your ground the less you go in the easier it will be tomorrow night.
Sometimes my son still wants to sleep with us and he is also a twin so from conception he hasnt been alone. His Dad doesnt seem to mind so much on those nights and I sleep on the couch and will move him in the middle of the night.
There are many different methods to bed training. This has been ongoing for me and it seems to only get better and you will eventually sleep again.
(I wrote all this thinking your son was 6Months) 6 weeks is easier- no pillows though, instead use swadling blankets.