Help-How many calories do I need?

Hoping someone will help me out here-I am having a hard time figuring out how many calories I really need, I have tried online calculators but they all say something different, and I am unsure about my activity level.  I am 5'9, 24 f, 155lbs, about a 31' waist with a med/large frame and quite a bit of muscle.  I run 6 days a week, between 6 and 7 km a day.  I am on my feet most of the day, at least 8 hours.  I ride horses for a living, and am in the saddle for an average of 2 hours a day.  I exert enough energy riding to sweat, and strip down to a teeshirt in the winter.  I walk an average of 1 hour a day, and bike an average of 30 min a day (10k).  I have been dieting the last year after rapid weight gain due to taking the pill, before that I never really worried about what I ate, but cutting back to 2000 cals seemed like starvation!  I ended up going down to about 1800 at the lowest point.  I am eating much, much healthier than I used to, but am feeling fatigued alot of the time, and by 9pm I am totally exhausted(can't even keep my eyes open).  I am eating between 2400 and 2700 now, am I on track?

Any help, insight, experiences...all appreciated.  Thanks in advance! 

The calculator I use gives me a starting point of 2700 for a 'very active' person with your stats.  However I think, if you're feeling fatigued on that amount, you should bump it up a little each day and see what happens.   You could end up at 3000+ quite easily.  If your weight stays the same, it's not too much food.   Nutrition is going to help as well.... make sure your food has plenty of variety and a good content of things like iron, B vitamins etc.  

I should think your schedule explains why you feel fatigued by 9pm...  If you think it's abnormal, however, and if extra energy and better nutrition don't resolve the matter then do talk to your doctor.  Fatigue can be symptomatic of various medical conditions.

I also horseback ride.  I where a heart rate monitor when I go to the barn.  Start it when I start tacking up and stop it after I put the horse away.  I ride hunter jumper and generally am actually on the horse for about an hour.  I'm 23 5'5 140lbs and in 2 hours generally burn anywhere from 600-1200 calories (more calories on harder horses)

just to give you an idea of what your burning just by being in the saddle.

Thanks both of you for the great info, that really helps!  Liz, I had no idea how many calories I was actually burning working with the horses, very interesting.  Gi-jane, I will try bumping my cals up a bit, 3000 seems like so much (the only people talking anywhere close to that number here are guys!) but I will give it a try.  I have been wondering about a possible iron deficiency, I will make a trip to the doctors if things don't improve.