so frustrated!!!

So this morning me and SO had about 15 mins to do the BD before I had to leave for work. So we get started, use a good amount of preseed and everything. It was great but he did not ejaculate! I'm so frustrated! I know that I shouldn't be, we were rushed but I still don't understand why this happens every now and then. It's usually never a problem. Does this happen with any of you ladies? And if so how do u feel about it?