
Congratulations on your upcoming marriage in April.
Although you cannot file for his green card paperwork based on marriage to a U.S. citizen prior to your marriage, you can certainly plan and prepare everything now. There is no reason not to review and analyze all of the issues of the case now and start to prepare things in advance of your wedding in April.
In general, everyone's case is specific so it is probably a good idea to at least consult with an immigration attorney about your specific case and issues.
You can find excellent info on the green card process based on marriage at:
http://www.familytousa.com/green-card-through-marriage-ad/
Every case is different though, and each case has its own issues such as affidavit of support and other eligibility concerns. Also, pursuing a green card while in F-1 status also entails very specific issues and concerns about travel and not abandoning the green card paperwork while it is in progress.
I recommend consulting with an immigration attorney to understand all of these issues and to develop a proper case plan for your and your fiancee.
Regards,
Andrew M. Wilson, Esq.
Serotte Reich Wilson, LLP