helloo der is absolutely nothin to worry...ur growth spurt is still yet to happen nd am sure ul gain stil more height...jus eat balanced diet good mixture of carb nd protein....lots of water...i would suggest not to do all d vigorous exercises at ur age as its ur growing age...go easy wid ur exercises...nd d weight gain is probably because of d muscle mass which is building up as a result of d exercises u do....hope dis helps