How much exercise is too much?

So I am an 18 year old girl and I have been having arguments with my friends about how much I exercise. I exercise about 6 days a week. I do kickboxing two days a week, 1 hr worth of cardio 2 days a week (keeping my heart rate within a 136-154 zone) and then intense running for 30 min 2 days week. Is that too much?