Baby waking up every hour in snoo or not

Baby is 16 weeks. We co-slept since the very beginning as he refused to sleep in his own bed. At about 13 weeks we got the snoo, and baby started sleeping 4 to 5 hour stretches, and we thought we are finally going to have some decent sleep. But for the last few nights things got worse again. He goes to sleep anywhere between 8 and 9pm. He consistently wakes up just before midnight, and he is fully awake, not just fussing. I feed him and settle him back to sleep. But other he is back in the snoo or in bed with me, he wakes up every hour! The only thing that helps in nursing him back to sleep. Is it sleep regression? Or what is going on?