Didn’t say he loved me?

Okay so my boyfriend is in marine basic training rn he gets out in about a month. Anyways, for the past month I’ve noticed his letters are becoming less frequent and when I do get one it’s really short. Today I finally got a letter after 3 weeks and he didn’t mention he loved me or ask how I was doing.

Am I being over dramatic about this? Or is it reasonable for me to be upset?