^ Uhhh, you sure about that?
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Get tested like ticktock said. Also, I hope you get yourself tested for other STDs and STIs than just HIV/AIDS.
In terms of keeping positive, you can try changing your attitude, contracting HIV isn't the end of the world, you can find examples of people living with it.
Try to immerse yourself in positive stuff, funny movies, motivational tapes, funny stories/books, that sorta thing. I'm sure other people can offer you more advice.