Sleepless baby

Hi mums.
Just need a little help.
My 1 year old son has always been a great sleeper. (Dont hate me yet)
For the last 5 weeks, he has been waking up screaming throughout the night. And i do mean screaming. Nothing in his routine has changed, none of the type of foods he eats has changed. Everything is the same. Down to the type of Pjamas he has been wearing and temperature in his room.
He is perfect throughout the day. Eats, poops, drinks, plays.. normal stuff.. no dramas.. but at night, hes in bed at 7pm, then at 12:30 near enough on the dot he starts.
Tonight so far (1:50am) we're up to number 4. Usually its about 7. The worst has been 9 times.
Ive resorted to giving him a bottle, which he hasnt had for maybe 4 months or so, that didn't work, I've rocked him (which i never do) didnt work, I've even crept into his room at 12am, and waited to see if anything happens.. nothing happens.. he still wakes. I change his bum to make him more comfy, still wakes again.
I thought it may be his teeth, but there aren't any other signs.
Im not fussed about me not sleeping, there is coffee and red bull for me. Just my poor little mate. I'd hate to think hes in pain.
Literally just this second I've thiugh of silent reflux which ill look into, but any other suggestions on what may be causing it would be greatly alprecisted.
(Make that number 5 out of bed)