Harm from doing that?
I realy don't know, but my first thougth is that maybe is not very safe to do it. I mean some people enjoy peeing all over each other, i don't like that but i don't hate it, and i see no harm in doing that, since you can take a shower and that's it, you are clean again, but if you pee inside your g/f, i think it will be realy hard to clean the mess later and she might get an infection or something, or am i wrong?
About the breasts, well, the guys here already give you the best options
. Good luck.