Mom is too involved in my life?

This is a bit lengthy so I apologize in advance.
My significant other and I have been together for 7 years now. We have a 4 year old and a 2 month old child. We haven't gotten married due to personal reasons, and I feel like I shouldn't have to explain it to anyone.
My mom on the other hand brings it up quite often and is very vocal about it. It has gotten to the point where she brought it up in front of my boyfriend and he wasn't happy she was commenting about it. She recently got upset with me over the fact that I traded in the car they helped me co-sign 8 years ago. We needed a bigger car and both of us co-signed it. When I told my mom I thought she would be happy but instead she told me I am dumb for allowing him to take that car, that I am not married to him and that nothing belongs to me. She can be very judgmental and petty.
She is overly sensitive and if you try to calmly talk to her and defend yourself she bursts into tears and calls me immature.
Last month I told her that we sent in $20,000 for our mortgage payment to pay off our house faster and she told me that I shouldn't be investing my money into a home when I am not married to him.
I am so tired of it. Frankly I just want to tell her to mind her own business. Instead of her being happy for us she chooses to be negative and wants to control my life.
How can I address this or should I just let it settle and ignore it?
Added (1). I have also told her couple of times not to mention the fact we are not married because its our personal choice but she still does it. We have had our fair share of problems but who doesn't?
She always compares me to other women and says things like "XYZ is on her 3rd marriage and each man legally married her" etc.
I hate being compared to others by my own mother. I have always been close to my parents but this is making me re-think my closeness with her.
Added (2). Both cars we own are in both of our names and so is the house.

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