13 month old keeps waking up every night at the same time!!!!

Why do they do this 🥺😖

He used to sleep through the night (7pm to 5.30am) but for the past 3 months hes been waking up crying between 12.30-2.30am and will not sleep again unless I hold him or he sleeping next to me.

At first I thought it was a leap and will pass

Buts its 3 months now and on going!!!!!

Why???

And how do I get him back to sleeping through??

Help .. I just want one night where I can sleep through