Alternating constipation and diarrhoea

I have had SIBO for a while and have had a bit of a bad time. I’m not gonna lie I’m a bit clueless on how to approach it as I was a bit confused by the guidance given by my nutritionist. I had low stomach acid and wasn’t digesting food well, so I was put on HCL / stomach acid tablets which definitely helped with bloating. I also was eating pretty low fibre and low fodmap, but still eating some less offensive vegetables to keep stools regular.

A couple of weeks ago I stopped pooping - no idea why, no change in diet, water intake etc - and didn’t have a bowel movement for a week (I normally poop every day without fail). I had to go to the ER due to pain, and they prescribed me lactulose, which did the trick (basically liquified everything), I was taking macrogol before this and it didn’t really help, but lactulose did. Now, I’m constipated again and feel like I need a lot of laxatives just to be able to poop at all. I’m so baffled about what to do as I’ve been told don’t have lots of fibre on SIBO diet but everywhere you look tells you to eat more fibre. Any ideas on how to approach this? It feels like I’m just ping-ponging between not constipation and diarrhea. Thank you in advance :)