Sounds normal to what all mine did - and only two sleep through now (the 6 year old and the nearly 5 year old - and this has only been in the last 3 weeks!)

Anyway I can't really help cos I never found a solution however I stopped very early trying for hours to put my kid to sleep as a baby. If it takes longer than 15 minutes then I get them up again. I found that rocking, patting etc for ages just made me more frustrated and then baby feels your frustration etc - so I got all mine up again. Try for 15 minutes, get them up for 15 minutes for a play. Usually by the second cycle they would fall asleep within the 15 minutes but if they didn't I think it helped my mental state to see an end - because I hated rocking and patting for ages with no end in sight.