6 month old waking up

My son was sleeping usually 11-12 hrs per night from 7am-6am or til 7am.

This past week he has been waking up at 2am and 5am. Then last night it was 1am and 5am.

He’s been teething for a long time so I don’t think its that bc it it was it would’ve affected him already but maybe not idk.

My husband thinks he’s really hungry (we are waiting until he’s exactly 6 months old next week per the recommendation of the pediatrician...or maybe we should just start now?)

Anyone else have this happen with their LO...great sleeper then started waking up around 6 months? What are the reasons this happens?