Baby won’t sleep HELP!

Olivia • Mommy to a baby boy 💙

My sons almost 4 months old and has always slept 8 pm to around 2 or 3, then back down till 7. He’s such a great sleeper up until Monday. For the last week hes waking up at least every hour. No routine has changed. Why could this be?! He’s drooling a ton, is it teething? I’ve heard of the 4 month sleep regression, but I’m not too sure about that. He literally won’t sleep more than an hour at a time. Any advice? 😩