You can request a titer- it's a test that will tell you if you've ever been exposed and have the antibodies already in your body to fight it. I never had it and never got immunized- got the titer and found out I've already been exposed in the past and am immune now.
Also if you never caught it as a child you may already be immune to it. My mum said when I was younger she used to send me to other children's houses who had chicken pox and I never caught it. I've still never had it and my doctor said it's unlikely I will but I'm more at risk of something called shingles when I'm older.
Not always true...
My child's Dr said that since my children we're both given their shots for pox, that they will never... NEVER get it.
I freaked out cause my 6 yo daughter had a rash so I took her to the Dr thinking that's what is was. (It just just a great rash) but she explained they will never get it.
If you know you had chicken pox as a child, you're immune. The problem comes in if you didn't have chicken pox as a child, OR if you got the vaccine which doesn't protect you for life. If you had chicken pox as a child, you're protected for life.