9 month old won't sleep unless held

Ladies I need help! Our son will not sleep in his crib at night. He is in his own room, has been since 5 months, but now he won't sleep. It's been bad the last few nights but has been happening on and off for weeks. As soon as we put him down he is screaming and if we ever do get lucky enough to have a peaceful put down...it lasts 10 minutes tops. The only way to get him to sleep is if my husband or I hold him but even then, if we try to put him down..nope!

Things we have already tried: light and sound machine, humidifier, ceiling fan on low, calming bath soap and lotion, no afternoon nap, cry it out, putting my shirt under the sheet so he has my scent...hell my husband left his phone next to the crib on youtube out of desperation.

I'm not sure what has changed. He was sleeping 5-7 hours before waking up to nurse then another 4-6 hours after. It's passed the point of my husband and I being tired, our son needs to sleep. He has his bottom two teeth and does not seem bothered by them. I have noticed him chewing his thumb at times but nothing extreme. He doesn't act sick or like something is wrong during the day and does take naps. Although they are typically short. We go to the doctor next week for a check up but I thought I would come here for advice before. I'm running out of ideas!