That's actually a fairly common thing. That lil guy needs to be continually encouraged, stopping to put the condom on causes him to lose some interest. I'd say that you work as quickly as you can and have your girl keep the intensity going through kissing, heavy petting or whatever works. Perfectly ok to masturbate a bit after its on, that should bring things back to life. One question, is this a new problem? Are either of you virgins and could this be related to nerves or performance anxiety? If so, the issue isn't totally related to the condom. Let us know and we'll see if we can help with that as well.