Too soon to tell if he is or is not into you and this relationship.... most guys like to take it slow and do not like it when the female is the aggressor right off the back - not that you are, but in his eyes (the male way of seeing things) your constant calling may have him scared that you want more than he is willing (or) able to give right now.
AND - then again I could be so far off base and he has just been busy - for it has only been 4 days and most of them are working days.... breathe and give it some more time - another week.

LoVe,
Rhapsody -