I can understand about the mess part. A man likely doesn't know how uncomfortable it can be to find things constantly dribbling down your leg - sometimes not just immediately after, but like the next day. And if you have sex a lot, then that means you can have this happening on a daily basis and it can be uncomfortable.
In lieu of condoms, some things you can try instead - clean up immediately after sex, go to the bathroom and relieve yourself immediately afterward (and sit upright there for a little bit allowing gravity to help you), wear a liner/pad immediately after sex, wear a panty liner the next day, or use a tampon immediately after to help soak up some of the 'mess'. Oh, and for immediately afterward - keeping some wipes close by and a towel so you can make it in to the bathroom for all of the other ablutions is also helpful.
Oh, and maybe if he sees all of this cleaning and you express concern about it, he might be willing to wear one some of the time. This is the compromise we have in place. For instance, if I've got something really hopping the next day, my H will often just volunteer to wear one because he knows it can be a pain in the a$$ for me to deal with it as much as I have to.