Was the baptism in the LDS church?
In what church were you baptized?
It might not be.
Many LDS were formerly some sort of protestant. It is possible that the OP was baptized in a protestant church before becoming LDS. If so, the protestant baptism is valid.
LOL, pay attention, guys.

He said he had been baptized Lutheran in his infancy well before those two replies:
I was christened a Lutheran as an infant and baptized in the name of the father and the son and the holy ghost as a mormon when i was 15. will i have to re-confess if i am not required to be baptized again? 51 years of confession is going to take a while!
thank you all for your answers!!! i will look up general confession in my copy of the catechism. (I have been studying while i wait for rcia!)
Welcome home! Praise be to God Who has brought you to His Church.
1ke did a great job answering your questions, so I needn’t say more.
Then why is their baptism invalid?
OK. Do you have any idea what the Church’s reasoning was? The Dubium is a bit terse.
Yes, I know why Rome made that judgment.
Baptism, like all Sacraments, isn’t magic. Yes, the right words are necessary, but it’s not *about *the words themselves. It’s not the repetition of certain syllables that makes the form valid, it’s the meaning behind those correct words.
Mormon teaching on God is radically different from orthodox Christian teaching, so when they say “I baptize in the name of the Father, and of the Son, and of the Holy Ghost,” they’re using the same words but with
absolutely different meanings.
They believe that the Father, the Son, and the Spirit are three distinct beings united in will. God the Father, in Mormon teaching, has a physical body, and a wife, the Heavenly Mother. God the Son - Jesus - is literally the biological son of God the Father and the Heavenly Mother. Furthermore, “God the Father” was once what we are now, and he achieved godhood in much the same way devout Mormons can.
So, as you can see, the words have completely different meanings. They might as well be baptizing in the name of the Tomato, the Potato, and the Radish for all the good it’ll do.