Alot of things can be said about this and my mind has also been on the subject.If a condom was worn then *make sure its not very tight as to restrain but fits nicely,maybe 1 size larger* then the lack of semen would not be noticed or questioned (as long as you disgard it without the person seeing its contents) .As for pumping,there are many ways this can be done as well,if you are sneaky,you can make it seem to play with your scrotum while going so slowly,not going to fast as a man *depending on how turned on he is-so go by this* does not normally rise at a fast
rate.so maybe during oral, *play* with them and if comments are made just state *this is what i like* or if you do not wish to try it,then during a make out session,make it seem you have a *rise* then request a fast bathroom break in which to pump then do a blush from the *sudden* rise and go from there.There are many natural ways to deal with this situations and takes time to think on.but it is possible to do