Im f, 5'6(tall) , thin, long arms&legs, hands r big w/long fingers &are flexible, but my body is not flexible, narrow face&jaw, do i have marfan syndrome?

possibly: Possibly, but there are several forms. Evaluation of vascular health would be reasonable.

Can be cryptic: Most people who are thin do not have a connective tissue disease (marfan syndrome.) there is a formal diagnostic approach for suspected Marfan syndrome, though, and it is worth reading. Here is a link to a helpful site: http://www.Marfan.Org/expectations/diagnosis.