I haven't read the other replies but I'm Catholic and breastfed my babies under a very light blanket in the nursery/cryroom. I rarely got a second glance. During the summers it got very hot in that room and I asked the lady in charge of Sacraments and Worship if there was another place I could nurse so I could remove the blanket. She was wonderful and suggested a room right off the cryroom that wasn't in use. She also said that if that was too hot, I could go in what used to be the pastor's apartment which was still occasionally used for visiting priests but mostly empty. Lots of comfy chairs up there!
I would be EXTREMELY surprised that the Catholic Church has any kind of rules on breastfeeding. Although, i agree with you that if you were near any older folks who were praying, the cute little suckling noises might cause them to lose their place on the rosary..... I know that when i start breastfeeding in front of my dad (who is very modest, rather conservative but pro-breastfeeding), he kind of misses a beat and forgets what he is saying in an effort to not look. Oops, sorry dad....
If your husband is that shy about it, rather than get into an argument about it, simply call over to the church tomorrow and ask if there is someplace comfortable where a breastfeeding mom can sit in privacy during mass. I'd be surprised if they weren't willing to help!
" I object to violence because when it appears to do good, the good is only temporary; the evil it does is permanent." Mahatma Gandhi
"This is the ultimate weakness of violence: It multiplies evil and violence in the universe. It doesn't solve any problems." Martin Luther King, Jr.