Ugh both of my kids went through nine month horrors.

DS has been a horror sleep-wise since 4 months (sorry buddy!) but we went through the absolute worst of it at 8-9 months. Waking up hourly, all night every night for about two months. I nearly sold him on ebay my god it was bad.

DD was a perfect sleeper from birth - slept through at 10 weeks and has done so to this day except when she's sick. AND except for when she was 9 months lol. She went through about three weeks where she'd wake up every night at about 11 and would NOT go back to sleep for anything. We thought that was pretty bad until we had DS

Both of them got over it, one just took ALOT longer than the other. If your bub was a good sleeper previously then I'd bet if you just stay consistent with what he was used to before, he'll settle down again sooner rather than later hopefully! Hang in there.