I am no doctor I will not say that I am 100% correct and neither can any other web site tell you that they are 100% either. You can get pregnant off of pre ejaculation. Your chances are lower but you can become pregnant. Because the pre ejaculation was on his hand it had a chance to hit the air. Sperm dies very quickly when it is exposed to the air, and on a second note since you were wearing tampon on the time that he fingered you if there were any live sperm on his fingers the tampon would have stopped it.
But I am like 99.999999999999% sure that you are not pregnant. You can relax hun