Finishing too quick

So lately my boyfriend has been finishing SOOOO quickly. He used to be able to last quite a while about a month ago..now he only lasts maybe 3 minutes. He even pulls out and takes a few second if he’s getting close. He is pretty embarrassed about it but I’m not making a big deal about it. He said this has never happened to him before. Any ideas of why this is happening or what we can do to help him last longer?