J. - Oh honey, I feel your pain.
I remember when my son did that. He was older than 6 months, probably more like 14 months. It was three sleep deprived weeks for me and my husband (who also gets up at 5AM). I finally took him to the pediatrician to see if there was anything physically wrong with him. They said, nothing was wrong, but that he had learned he could control us by not sleeping and he was practising his new talent. The Dr. told us to do the Ferber Method, go to him in 5 minutes, check him - give him a hug, tell him to go to sleep. Then wait 10 mintues, repeat, extending 5 minutes longer each time. It took us another 4 nights to finally get him to go to sleep within 20 minutes of putting him down.
At 6 months, it is not to early to start a routine - same thing every night. I have two boys now and I really believe in the routine to prepare them for what they can expect. Here are some things we do: 1. Bath not everynight, but we use the Johnson Bedtime Lavendar wash and lotion - so it stimulates their sense of smell and they associate it with bedtime. 2. PJ's the same parent everynight puts on the boys PJ's (bedtime is my husband's THING - I do the rest LOL!). 3. Night Night Bottle (or nursing for you) to top them off and get them through the night. 4. Cuddle Time - we started singing the same songs to our oldest in the same order(rock-a-bye baby,twinkle twinkle, etc. . As he got older we switched to books with a bedtime theme (Good Night Moon, It's Time for Bed etc.) 5. We have a CD player in the baby's room that plays Kenny Loggins Return to Pooh Corner. We put it on every time we put the baby down to sleep, for a nap, if he wakes up in the middle of the night - hoping that the same music will subconciously trigger him to go back to sleep.
I am sure you already have some type of routine for your son. But these were the things that worked for us. After we had a second child, then I started doing some of the things for the older one and we started switching back and forth. I have friends who's children will only go to sleep if Mommy puts them to bed. For me, it would be awful if my child could only go to sleep if I put him to bed. I would never have a night off, and as a SAHM, I need to get out with my friends every now and again for my sanity!.
Also, you might want to take him to the Dr. just to be sure all is okay. Some illnesses only show up(or get worse) when the baby is in a horizontal position, like ear infections, reflux etc. And at 6 months, he is probably getting some teeth, which might be bothering him too.
And finally, I am a stay at home Mom, and my husband works(as an Engineer) - but these are his children too. I work just as hard as he does, or harder because I am dealing with creatures who cannot communicate with me and require my constant attention. I need sleep just as much, if not more than he does. I ask my husband to help me at night if the kids are up. He takes one night and I take the next. OR we take turns if they wake up multiple times during the night. I let him know what needs to be done around the house. He helps with laundry, cleaning the kitchen after dinner or whatever I tell him needs to get accomplished before he goes to sleep. And he still has over 1 1/2 acres of lawn to mow and other outside things to do. But these kids are both of our responsibilities and we have to help each other out or one of us will get burned out and become very unhappy. We have to stick together or our marriage will suffer. So, please ask for help from your husband - he loves you and your son and these years of infancy are so short that you two can get through them much easier as a team.
I hope you get some relief soon. Best of luck to you.
W.