Congrats on the new snake and happy birthday!
It looks like you have a really nice looking Anerythristic (type A) there. I really like those clean colors.
As far as sex goes, someone experienced can sex it for you, if you know such a person or can locate someone. Also, there are other methods like belly scute (scales?) counts and a way to guess based on the shape of the tail. I'm no expert on any of those methods. I'm sure there are lots of threads if you do a search for sexing snakes etc.
Or if you can throw up some good pics of the underside of the tail from a little ways above the vent down close to the tail tip, I'm sure people would be glad to take a stab at telling you what you have.
Good luck with him/her!