My mom has lied to me my whole life

This is sorta complicated, so bear with me. When I was a teenager and went to apply for my driver's license, I realized that the last name on my birth certificate was different than the last name on my social security card. Obviously, this was quite a surprise. My father died when I was 2 years old, so my mother explained this by saying that the hospital had mistakenly put her maiden name as my last name (when this happened she claimed this was the first time she's even realized that my last name on the birth cert was not correct...). I'm sure you've already noticed a contradiction: if she didn't know the name was different until that day, how did she know the hospital made a mistake? Anyhow, I digress...The license place said they had to use the name on my birth certificate, so at the age of 17 my last name suddenly changed. The license place suggested from then on I hyphenate my last name to show both names that way I wouldn't have issues with registering for college and all the billion other things you have to do with both your birth certificate, social security number and your driver's license as proof of identity. Anyhow, I just accepted what my mom said, or really, I just let it go. It has bothered me greatly, but since my father had died so long ago, it wasn't like I could get him to have my certificate changed.

Fast forward to today. I finally went to the social security office to get a new card with the corrected name because I need to put my name on my husband's checking and they wouldn't accept the two different names...anyhow. I give the lady my stuff and explain that I need to change the name to the name I've gone by since 17. She asks me what my father's name was and I tell her Joe Smith (or whatever) and she goes "OH". And of course I was like "what"? And she says, "well it shows here than in 1976 (when I was nearly 1 year old) that your last name was changed by your mother". Which this is clearly surprising to me since she claimed to have never realized the mistake until after my father died. So, I said, what name did it used to have and she told me that it was my mom's maiden name (I'll use Jones for the sake of little story and I'll use Smith as my dad's last name). So apparently when I was born my social security card was issued with my mom's maiden name (just as my birth certificate indicated), but in 1976 she went to the office and had it changed. She changed my last name on the card to Smith from Jones. At the same time, she also changed who was identified as my FATHER. Originally it was a totally different name (I'll say it was James A. Brown). So I ask the lady if I could have a copy of this information and she said she wasn't allowed to tell me (at this point she hadn't told me the original father's name). So I spent about an hour chit chatting and getting friendly with her in an attempt to get her to tell me what my REAL FATHER'S NAME WAS. When I got all done with changing my social security card I had to sign some forms and she passes me this piece of paper and says, "I cannot let you have this, but if you wrote down the name there's nothing I can do about it." So I see that my real father's name is James A. Brown.

I proceed to walk outside, sit in my car and cry hysterically. I've gone my entire life without a father. The man I thought was my father died in a motor cycle wreck when I was only 2 years old. At several points in my life I have attempted to question my mom about the person I thought was my father but she has never really told me much of anything about him. Then about 3 years ago I happened to find that my mother and my supposed father weren't married until about a year after I was born. When I found this out, I asked my mom how this was (she had always told me she was married before I was born) and she SWEARS that she cannot remember and she's certain she was married before I was born and she has NO IDEA how they could be showing a different marriage date. So, I guess I've always wondered.

Anyway, I called her this afternoon to confront her with all of this stuff and she initially acted like I was telling her I had 2 heads and kept swearing she had no clue what I was talking about and said she never hear of James A. Brown and the SS office must have made a mistake. I pointed out all of the things I have outlined above and she started sounding really hysterical and kept repeating that "Joe Smith is your father" "Joe Smith is your father"...over and over. Again I tried to ask how this other name is recorded as my father and she says "That name should have never been on there!" So voila! She has revealed she DOES know James A. Brown and I ask who he is and she says its none of my damn business. Of course, I tell her it is my business and it ends up with her screaming at me and hanging up the phone.

So here I sit. 33 years old and find out today that the person I believed to be my father is in all probability not my father and that my actual father is alive somewhere. I've lived my entire life without a father and she refuses to tell me anything. What would you do? She is not going to give me more information, but I do know that a few other people may know (my ex-step dad for one). I need to know the truth. How should I go about this? Do you think there is anyway to compel her to tell me?

I'm seriously on the verge of a nervous break-down. Aside from my brother dying, this is the worse pull the carpet out from under my feet situation that has ever happened to me. I don't know how to function. I don't know what to do.