Baby name feels ruined

Ever since we told my MIL we were pregnant she's been sending us baby names. I tried to just ignore it because my fiance and I know she's just excited.. Then at the gender reveal she brought us a list of over 100 names printed and cut out, and a name fell out started joking around saying that was the name we had to use. Once the gender was revealed then she started pushing to use the names for that gender in the box. This whole situation is just really stressful since my fiance and I can't agree on many names. We finally agreed on a name because it was really frustrating me that his sister started sending names too. I wanted to keep the name secret so no one would ruin it, and so my fiance wouldn't change his mind. But I thought I may be exaggerating so I told my fiance we could tell his family, which was a mistake. My MIL and SIL began to make fun of the name and are trying to pick out the middle name. I ended up crying for like two hours and it's to the point where I don't even want to talk to my fiance about names and I really don't want to use the name now. It just feels like his family crossing a boundary taking over the experience of naming our first child, and my fiance is close to his family so he doesn't see it as a big deal.