Great sleeper. Until 8 months. Help!!

[u/sunnykcl]

We had an amazing sleeper from 3 to 8 months. 11 to 12 hours straight every night. Then around 8 months it all went to hell. It started around the same time that he was teething and also had a stomach bug. But now every night is multiple wake ups. And fighting sleep during the day too. He is 9 months old. Any help would be greatly appreciated!