sleep regression or teething!!!??? help!

Dani
My son is 8 months old. He is my first which is why I'm asking this question. 
He has not been sleeping through the night for the last few days and cries when I put him down for a nap even when I know he is extremely tired!!! 
He has been climbing and trying to walk so I figure maybe he's exhausting more energy causing him to be more tired but he won't sleep. 
My pediatrician is not clear whether he is teething or not and is saying he is going through a growth spurt, which very well may be happening. Just curious on what's going on. He has also been so much more clingy. He crawls/walks to me for me to hold him constantly. 
He has also not done this before. He's always gone down with no issues and is very calm and content.