how a relationship can be 'complicated' when it's still in its infancy.

It implies that the one who thinks it's complicated is unsure of the other ones feelings towards them. A one-sided complication?

He loves me, He loves me not, He loves me, He loves me not.

Bit like at the youth club when you had a crush on some guy, but didn't know if he would ever ask you out and didn't know how to get him to do so. Now THAT was complicated! :D