8/9 month old sleep help!

[GooseandSunshine]

Desperately after some advice - DS is 9 months tomorrow and has never been a great sleeper, it all settled down at about 5/6 months but has recently gotten worse and I can't figure out what is going on.
He had a phase (2/3 weeks ago) of screaming inconsolably for about an hour and a half when I put him down for the night. This then changed to screaming in the middle of the night for an hour or so. None of the usuals would work (feeding, cuddles, tummy strokes, sshing). This is still going on but I've started cosleeping when it kicks off as this is the only way to get him to calm down somewhat and to get some sleep.
For context, he usually wakes a couple of times for feeds in the night but used to go straight back to sleep after them. He self settles at the start of the night. He's recently transitioned to 2 naps, will do 1 hour - 2 hours per nap, we cap total day sleep at 3 hours.
I can't for the life of me work out if it's developmental, over/ undertired or what. Any help much appreciated!

At 8 months they have separation anxiety and it's a bloody nightmare. I used to just feed him in the night and rock him back to sleep. You say you're capping his naps. Is he not getting enough sleep overall because daytime sleep really affects nighttime sleep

@Geometry Dash Listening to you, I feel quite sorry for this child's health. Sleeping little for too long is an alarming condition. You can take your baby to the hospital for a more thorough examination instead of describing the situation based on appearance. On here, people only give rough advice and cannot be 100% accurate. Wish the baby a speedy recovery.