ah, so your boyfriend is coptic?
if you are going to join the coptic church, do it to deepen your relationship with God.
and then after that see how the relationship is going.
because if you are both heading in the same direction spiritually, it is the best thing for any relationship.
what i mean is that if you are both interested in orthodox Christianity,
then consider becoming orthodox as a separate issue between you and God,
and then see how your relationship adjusts to this change in you.
you may find (as one friend of mine did) that you find something amazing,
but he may not share your new enthusiasm as much as you expect.
on the other hand, if he is really interested in attending church and praying a lot and relating to God
and you are not, this is likely to lead to problems in the relationship (not the age difference).
also if neither of you are very interested in the church, don't convert for marriage.
you can get married outside the church for visa purposes, and if you are not interested in attending church,
then you won't mind not taking part fully in church life after marriage either.
so, in summary, don't worry about age differences.
do seriously consider your relationship with God; this is more important.
(having said that, if you are 63 and he is 19, you may want to make sure you don't see him subconsciously as a grandchild - i expect this is not your case)
may God guide you and lead you in to the fullness of His grace and peace