I heard somewhere that scientists made sm kind of "replacement" for
 

semen made from the stem cells. Does that? mean a woman can get another woman pregnant? Or a woman can get herself pregnant? It's really weird...

stem cells are different from egg cells. egg cells are the one's that come from women.
I haven't heard about this yet but I think it might just be something related to genetics wherein you get a part of the semen to get the better traits of the father and leave the bad traits behind.
I'm sorry if I'm wrong but I don't think you can replace semen just yet.