It's amazing how dh's can accidentally add to the stress by suggesting if only we were strict about it everything would be OK!
Babies are all different, if your girls were OK then it's not because of anything you're doing/not doing, it's because that's the way your ds is - IMO :)
My dd has always (now 3yrs) been a terrible sleeper, and I could never put her down for a minute when she was a baby. In the end I decided to go with it and carried her round in a sling all the time, and co-slept - at least we all got some peace and some sleep that way.
If your ds is this kind of baby I think it unlikely he'll respond well to 'strictness' and it could just end up wearing you out.
It's up to you which way you want to go, but you have to trust your instincts. If you try and follow a path that inside you're not really happy with, it will end up in more unhappiness all round.
I'm a bit of a Dr Sears, attachment parenting fan. He says he developed the idea of attachment parenting (co-sleeping, baby-carrying etc.) because his dd was not like his previous 3 sons who had been 'easy' babies, so he had to find a new way of dealing with things.
It's very early days, don't be hard on yourself. I thought I was going to get it all right, because I'm an easygoing kind of person, and why would I not have an 'easy' baby. Instead I found it extremely difficult to cope, and was often in tears. But it did work out OK in the end, and now she's the most adorable bad sleeper in the world.