having a similar problem.. the only sure fire method i have discovered of getting DS2 to sleep, about the same age i guess of your little one.. is to put him to sleep on his tummy, with a dummy. I did try to be dummy free, but, i gave up. I figured, like Trish has said, if i kept struggling getting him to sleep, i was going to create an overtired baby, that couldnt sleep. At least he's into some vague 'routine' and sleeping during the day. As they say, sleep creates sleep. Evening time, i do have to rock him to sleep, but, as DH is home, i have the time to be able to do that.
Its funny, DS1 loved the bouncer and swing, DS2 hates them.
I read somewhere that they (babies) dont develope sleep association until they are about 10-12weeks old, so, i suggest, and my theory is, do what ever it takes now to get them to sleep, just to get that 'sleep creates sleep' thing happening, and hopefully, it will get easier as it they older.