How do i stop this sweating!? :(?

Ok basically i'll tell you a bit about me. I'm almost 16 years old and I sweat so much. I wear an antiperspirant everyday, one with a really good reputation 'Sure women, crystal clear.' I can't wear anything with sleeves because otherwise they end up being soaked through which is really frustrating because i'm one of those people who loves summery clothes and most of my summery clothes have a slight sleeve. I don't smoke, i don't drink, I dress appropriately for the weather, I have a healthy diet and drink enough water. I'm currently on microgynon 30 (the pill) for PMT reasons if that makes any difference, but I haven't found 'excessive sweating' as a side effect anywhere else. PLEASE help me here, it's getting to a point that I can't buy t-shirts I really like because they have a slight hint of a sleeve! It is also causing me to think extremely vigorously about what I wear each day. I'm currently doing my GCSE's and it's making my stress levels sky high together with the sweating. I currently have to wear uniform so it isn't so obvious as I wear black but I'm going to college in September when I will wear what I want and it becomes a bigger problem. Also, It's extremely embarrassing! please help? Oh, and it's only underarm sweating which is a problem.