What amount of calories should I consume?

Im 5ft 6 inches, female and weigh 8 & 1/2 stone. I currently work out 3 nights per week normally varing from kickboxing, aerobics or the gym. The problem is im unsure how many calories I should consume in a day in order to keep my weight around this. If anyone knows the answer I would greatly appreciate it!! Im becoming obsessed with counting calories and everything I eat and constantly weighing myself, if I had this answer then maybe I would relax a bit!!!