I know I'm always happy when my girlfriend wears soft shirts and no bra around the house. She's happy too. I don't mind if she wears them outside of the house, too. I know some people are all omg nipples=sexsexsex but it's really not a big deal :p
Why would he mind, it's not like you are flashing him. He's your boyfriend you're supposed to feel comfortable with him. Guys see girls with pokies all the time so don't worry about it. I get that awful garment off as soon as I possibly can when I get home. My guy has seen me with some pretty major pokies and has been able to control himself so far! I'm sure your guy will be able to as well. If you're still worried, come right out and ask him if it bothers him that he can see your nipples through your clothing
I have never worn one, but I know they are not the most comfortable things int he world... I always tell my girlfriend she should feel comfortable not wearing one when it is just us at home (not in a sexual way lol) I won't be wearing underwear when I just walk around in some cotton house pants!
Depends on who is looking, I'm sure your boyfriend doesn't mind, what guy wouldn't like to see nipples but if your around company or family that would be awkward and make him uncomfortable even if doesn't bother you
You are in your own private house hold and have no guests around while you do this I presume so no there is no problem, for the factor of your boyfriend I am sure he should be comfertable with this little thing and won't make a big deal about it if you have already had sex he has already seen them.