Is a Pescatarian diet good for me? (Details inside)

Hi I've been trying to eat a lot healthier and am starting a Pescatarian "diet"! Thing is, I'm not sure if it's good for me at this point in my life or if it would effect my body in ways that are not wanted.

• I am fifteen years old (turning 16 in three months)
• I exercise daily and before ate a semi healthy diet (15 year old boy, can't help myself to burgers and such)
• I am number one varsity at my school on the tennis team and play year round.
• Play tennis about everyday ranging from 1 to 4 hours.
• However, I tend to sweat more than the average joe, almost like a hyper-sweater.
• I have a lot of problems with cramping up during matches. (I drink 3 gatorades and 2 waters starting from 4 hours before a match. I eat bananas and tomatoes before and during a match while drinking from a gallon jug and sipping on a gatorade)
• Even though I run occasionally and am always active I tend to have low stamina and get fatigued by the second set. (If it's a decent to hard match) Is a Pescatarian diet going to be helpful or destructive?