Sorry Melissa - no magical answer
. I do have to say thou no matter when you chose to teach your lo indep sleep, there will always be a consequence (being loss of sleep and possibly overtired state).
If you want to get rid of this now - you will really have to be consistent and stop allowing him to fall asleep on you. I had the same issue with #2. She was a little younger though (4 months) but for the 1st 4 months I carried her around in the Babybjorn, rocked and BF her to sleep (as well as using the dummy excessively). Then finally I realised enough was enough and she needed to learn so I dedicated 2 weeks to her sleep and voila... things definitely improved.
His routine at 6 months should be more or less... 3 naps (2.5hrs max A time) so your day should look something like this:
7am - wake for the day
9am - nap 1 (1+hrs)
12.30ish - nap2 (1.5-2hrs)
4.30-5pm - catnap (45mins)
7ish - bedtime
If he is up from the nap earlier (like at 45mins) & you cannot extend the nap with pu/pd or soothing in the cot, then forget the nap, pick him up and wait till the next nap time but bring it forward. So instead of 12.30ish, have him napping around 12pm. Same for the catnap. I would suggest an earlier bedtime as well which will hopefully allow him to catch up on sleep in the meantime.
I think the suggestion from Little Lamb is a great one - maybe make a gradula wothdrawal... hold him less everyday until he is used to soothing himself to sleep.
hth
Layla