This could be my story with Liam all over again, we went through the exact same thing. For me I eventually got so tired of having to rock him off so vigourously that I just started to put him into his cot and pat him till he went to sleep. I know it is tough when you have a toddler to contend with as well, but after a few weeks of just sticking with patting instead of rocking he got the picture- and now he is much better. He goes to sleep in his cot every night, some night we still have to pat him but it is much better for my back and my sanity than rocking him.
I can so sympathise with not sleeping anywhere else, at that age Liam never slept in his pram, car seat, swing, rocker etc- but as you know he is a different baby now. Just believe that it will get better!