I'm no nutritionist... and if you've never been to one I recommend it. Don't let calories be your guide only guide. Instead focus on changes that you can implement gradually. Ex. If you drink soda, switch to diet, if you drink diet, stop and regardless focus on hydration (water is a good thing). Eat 5 to 6 times a day. Increase the servings of fruits, veggies and lean proteins you are consuming. I am 5 8, 170 at 11% body fat. The nutrition advice i have received has me focusing on trying to eat 3400 to 3800 calories. I plan my meals in advance (proactive instead of reactive and I keep a diet journal).
on a separate note I need to state up front I have no IDEA what I'm doing. I'm training for my first tri (oly distance in Sept) The reading was helpful, the site advice here is great, but most valuable has been getting involved with local clubs and talking with people who have already been there.
Good Luck!
Mark