Feeling upset over surprise baby shower again!!

She had mentioned if we had wanted one or planning to have one, and I told her no, i wanted to buy everything myself and enjoy my shopping and getting everything I wanted. So she was like oh ok cool.. Well she didn't care that that's how I wanted it to be 

She went on anyways and planned one without me knowing and surprised me. I was not happy the day it all went down. I felt I guess embarrassed and disrespected. . I was so glad when that day was over I had told her like omg why did you do that but in a ok way, but like strongly let her know it was not cool to do that. 

Well here I am again. About to have another baby in MAY. And my sister just mentioned that my mom and husbands aunt is about to plan a surprise baby shower in a few weeks 😡😠 I am furious that this is happening again and me not wanting it. I have the right to say no no no I don't want this. I've bought everything already and they know that. Why do they think this is ok to do. They know how I felt last time why do this again! I want to gather this weekend and let them know that I know ! What sucks is that my sister said please don't tell them I've told you.. And I don't want them to think bad about my sister letting me know. But I'm happy my sister did she knows how I feel about it.. It's them three that know so they will know 100% she told me 😑 I don't want them to be upset with her ! I'm gunna have a breakdown if I don't get this off my chest I can't let it happen I will blow up the day it happens and I don't want to make a scene or make them feel like I'm rude but that's gunna be the outcome 100% if it happens ! WHAT DO I DO HOW WOULD YOU HANDLE IT?