5 month old screams when put down to sleep

[teacupnic]

Finding things a bit difficult with my 5 month old DS at the moment. Every night when put in his cot to sleep, he screams. I don't mean fussing, or crying but ear-splitting, top of the lungs high pitched-screaming. I don't have a lot of friends who are parents so I don't know if this is normal but it doesn't feel it.

He was a poor sleeper as a tiny newborn, which we put down to colic. From around weeks 10-16 he was fantastic, waking once to feed between 7 and 7. Since then, we have an absolute battle getting him to sleep, in the manner I just mentioned, sometimes over an hour.

We have a bedtime routine of bath, feed, story, a quick cuddle from DH and I. DH then puts him in the cot, strokes/pats his tummy and plays some white noise. It doesn't seem to be working. If he's really, really screaming DH and I do pick him up.

What on earth is going on and more importantly, what can I try? We've tried shush-pat, am not a fan of cry it out, and often leave him a few moments to try and settle himself.

I am aware of the 4 month sleep regression and he's also got a tooth recently appeared, but how long could this go on?