Am I being petty?

A while ago my husband came across a good deal and got a Mercedes G Wagon. Awesome! Well he said he had got it for me but since I am a stay at home mom, he's the one who uses it. When we showed our family, he said he bought it for me and my family were surprised. My grandma even gave us $1000 for down payment. Which I feel bad for because she thought that car was for me. But here's the problem.

It's not mine. It's my husbands. When we argue he says I'm not taking HIS CAR. So after so many times of being told that, I realized this car isn't really mine. Which really upsets me because why tell me this and in reality that car is his. He pays it afterall so I really have no say.

I feel really bad for my grandma who gave us the money. What could possibly be going through her mind now? That we just made her feel bad for telling her we were trying to put a big down payment on the car but we were going to have to wait? We never told her with intentions of getting money. I feel like I need to pay her back?

Also, my family always makes fun of me for asking my grandmother to pick me up or drop me off when my husband is out working because we share one car. My uncles ask "where is your car?" "Why is he the one driving it?" And makes me feel bad.

The truth is, we can't afford another car right now. We really can't. We pay $700 a month for this Mercedes. But today my husband told me he was looking online for a car so I can have my own. And I sat there wondering like why am I the one looking for a car when HE said that Mercedes was for me. When I told him about what my family says he got pretty mad and said they don't understand that we share stuff. And when I said that they only say that because he said he had bought me that car for me, he said well you can keep that car and I'll look for another car for myself. This will never happened. Because he believes he gets more clients because of this expensive and luxury car he drives. He owns a construction company and often has to go over to clients houses to talk to them and go over jobs so when they see his car they Instantly thing he has a lot of money and why? Because his company is probably good, its all about looks.... whatever.

Am I being petty?