It is time to say goodbye to your friend.
He is in love with another woman and is marrying him, and now he will soon be dropping his female friends anyway.
Send them a congratulations card with $20 in it and wish them a long and happy marriage.
And get on with your life.
Understand that "in love" is NOT love.
Love is not about being attached to someone, nor about how we feel about them, not about wanting them, and even less about being happy when we are with them. ALL of these are selfish emotions, have nothing to do with love, and are what causes relationships to break up.
And since 50% of all marriages end in divorce, and only 12.5% end up being happy AFTER 20 years of maturing emotionally ... all your tears are over a fantasy you treasure that may not have anything to do with what the reality would be if you married him.
Don't go to his wedding and ruin it for everyone by crying. Besides, you are going to have to let go anyway, because his wife will know you love him and will start to put pressure on him to back off from you. Which he WILL do, because he wants his wife.