Praise be to Allaah.
Yes, you can become
Muslim and that will be the greatest decision that you can take in this
life, because of the happiness in the Hereafter that will result from that,
in sha Allaah (if Allaah wills). We would be happy to hear this news from
you in the near future.
If your boyfriend becomes Muslim, there is no
reason why he should not marry you, even if he is married to another woman,
if he is able for it financially and physically, and he thinks that he will
be able to treat you both fairly with regard to spending time with you,
spending on you and providing accommodation, and everything in which it is
possible to be fair. But if he fears that he cannot be fair, then he should
limit himself to only one wife, because Allaah says (interpretation of the
“then marry (other) women of your choice,
two or three, or four; but if you fear that you shall not be able to deal
justly (with them), then only one”
See also question no :
This applies if his first wife is Christian
or Jewish (from the people of the Book), because there is nothing wrong with
a Muslim man marrying a Christian or Jewish woman. But if she is of another
faith, if he becomes Muslim it will not be permissible for him to keep her
as his wife; she has to become Muslim or he has to leave her.
We ask Allaah to guide you to that in which
there is goodness, guidance and success.
And Allaah knows