Do you think Im getting an engagement ring for my birthday?

We have discussed marriage so I know its a possibility and my sister let slip that he has asked my mum for my ring size. I felt pretty certain that I was getting a ring for my birthday and he's said that he's pretty broke after getting my present but then he said he's had to pull some strings to get it delivered in time for my bday and then said he had to get it sent off to get something done to it. So that last thing has totally confused me cos surely if he bought a ring he would get it from a jewelers and why would he need to have it sent off? Do you have to send off rings to get the size altered or do they have stock in the shops? but then if he is getting it delivered you would think that he would have been able to select the size...gah! I wish my sister never told me, Im going crazy with anticipation! What are your thoughts? Do you think he's got me something else and what could it be?