Controlled crying

[Jellybean2017]

We have been having issues with DS sleep, won't nap unless in sling and with lots of movement, won't sleep unless laying across me, won't lay on back, won't take dummy, won't sleep in bouncy chair despite trying persistently. GP thought possibly reflux related due to constant crying in addition to to above. Tried gaviscon and ranitidine but no improvement. Referred to paediatrician.

Paediatrician said all the issues are down to sleep associations and we need to start controlled crying. DS is only four months old, this doesn't sound right as I think it's usually recommended to wait until six months at the very least. Does anyone have any advice? We have also been prescribed omeprazole even though paediatrician doesn't think it's reflux...? Surely controlled crying is a bad idea if it is reflux?

Weirdly he went down in his cot for an hour this morning with loud white noise on. Laying on his back. First time in months. Probably a one off. Thanks for all your advice 😊 a few things to consider.

4 months is very little and they have a 'sleep regression' around this time anyway.
Sleep training is controversial and I'd urge you to read up on it before making a decision (I decided not to after doing my own research because of the increased levels of cortisol and the theory that this can impact the child's mental wellbeing).
I don't think it's generally advised before 12 months either.
My DD would only fall asleep in the sling the until she was 1. I'd just transfer her onto her bed when she fell asleep. It's a tiring time, but as their body's mature issues like reflux do settle down.

Ditto the 4 month sleep regression. No sign of this with my first but we had a classic case with DS2, it was awful. He was another one who they kept diagnosing with reflux, I think it's just a bit of a 'catch all' diagnosis when a baby won't sleep and is unsettled.

Controlled crying is not for me and especially not for a baby as young as this.