OK ladies I need your help do you think I am in the wrong?

Tonight is my boyfriends cousins birthday and it's an adult party were no kids are allowed except the babies. I personally don't want to go and I keep telling them that I have no business going to an adult party right now when I cannot drink. They keep telling me to go and go socialize with other people. I was really considering it because they said I could bring my baby. Now I got this text message from my boyfriend's cousin and it really pissed me off. My son is five weeks old and I am nursing him. I produce enough milk to keep him well fed as of right now and want to continue nursing him as long as I can. Do you guys think I'm in the wrong for the way I responded? My 21st birthday is in two weeks and I'm sure I will then leave him with someone but as of right now I don't have the need to leave him.