How to tell my so we were pregnant but miscarriage

My love is in basic right now, he got to come home for Xmas well we had a oops and I found out I was pregnant 3weeks and 4 days but end up losing the pregnancy. He knows about a light positive but nothing more because it was a short phone call. His graduation is coming up and I don't have the money to go ): problem he got his hopes up so hight to see me now I'm letting him down by not being about to make it and I'll have to tell him over the phone about the pregnancy/ miscarriage .. I'm a mess .. but I don't know how to tell him over the phone.. I wish I didn't have to