In this case,baby doesn't mean "akachan", in Japanese we don't say so.
My baby, what are you doing now? : watashi no itoshii hito / taisetsu na hito, ima nani wo shiteiru no?
I miss you so much : watashi wa anata ga inakute totemo samishii
I love you more than anything.: watashi wa naniyori mo anata wo aishiteiru