Hi,
Sorry to hear you are having this prob. I haven't had it happened myself, but have red a bit about it lately and do know of someone recently having the same thing... What I red on the net it said to pay a quick visit to the Dr to get everything checked out (nothing to worry about though, sometimes our cycles just get out of whack!). The person I know that had the same thing went to the Dr, was put on some tab which got her cycle back on track. Things maybe a little different for you as your BF, but I'd go and have a quick check anyways.

Hope all goes well