Irregular period problem.. please help..?

i am a 16 year old .. 5'4..weighing 63 kgs.. i have been getting my periods since the age of 14 but they've never been regular.. i tend to miss a month in between.. there aren't any fixed no. of days between two cycles.. my mom is really worried about this and wants to consult the gynecologist regarding the same.. but i am really very scared to visit one.. what should i do? .. and yeah also i have gained around 13 kgs in the past two years..what could be the reasons for such irregular periods????