Help! I'm always constipated?

Right so I'm 16 and since I've been about 9 I've had to eat a high fibre diet. Recently though even with my high fibre diet I'm always constipated. Like I only have a bowel movement once or twice a week and have had to use laxatives a lot and it makes me really bloated. I do drink a lot of water and do a lot of exercise. Is this normal or could it be a serious health problem?