The easiest ways to determine the sex either by the shape and length of the tail or by probing the snake. Both methods are best done by someone that has had a bit of experience since the first requires seeing a number of snakes (or having multiples so that you can compare) and the second runs the risk of injuring the snake if you do it incorrectly.
pictures would help a little, but without a few animals for comparison at best it would be a guess. pictures, especially of younger animals, can be misleading as to the size of something. is there a reptile vet in your area? if so they should be able to probe your snake safely and for a small fee. searching google for pictures of side by side comparisons of florida kingsnakes of known sexes will help, but not provide a complete answer. try looking around your area for other snake keepers and make friends with them, you might get lucky and find someone with a set of probes thats adept at using them. good luck.
Simple visual comparison is inaccurate at best. Probing is definite, but must be done by someone that is well-experienced...an inexperienced person can both be incorrect, and permanently damage the snake.
Fluoroscopy/x0-ray is also accurate if the attending veterinarian knows what to look for, but it is not inexpensive.
maybe try find someone at a pet store to do it..that is if he's a reptile dude like th eone here who fools with reptiles, etc and knows what he's doing...otherwise check around your area for other people who may keep snakes..if no luck there then just try doing the tail trick.