i hope nothing is wrong

Hello. About starting yesterday ive been haveing this wiers pain in the chest. I dont know if its my heart. it might be. It only happens 2 or 3 times in a day. It fells like someone is grabbing my heart and applying slight pressure then letting go. Im only 17 years old. I have high Cholesterol. The doctor said to get more exersize and eat better. Ive been eating more chicken no red meat and lost of fruit and veggies. ive been doing more physical activites. MAybe it's gas im not sure. Can someone please let me know what this could be or what causeing it. Thanks