Vaginal swelling and discomfort in a young teen

I am 13 years old and I have been experiencing some vaginal discomfort for about a week. Since I masturbate almost every other day so naturally I notice when something was wrong. The very opening on the inside of my vagina it has swelled a bit, it does not feel hot or hurt when i touch it, but when i go to the bathroom it burns and stings really bad! They pain comes on and off all day, normally worse in the morning and midday and subsides before i go to bed (sometimes) otherwise its all the time. I just got my period (i have been getting it for 3 years now) and I noticed a tinny or metal smell, is this just from my period? And I really wondered what was going on in there, so i washed my hand and took a look. AND I COULD NOT EVEN GET MY ONE FINGER INSIDE which is very abnormal for me! if felt so swollen and the inside was very tight! The only time the pain is gone is when i use my clitoral vibrator and i just use it around and near the opening for a while, but that is all that seems to work. ( the pain is only gone for 10 mins anyway and then comes right back) What is this? what should i do? I really do not want to go to the doctors or tell my mom until i can come to a conclusion as to what it is. She is a nurse so she would help. Im just embarrassed. Also, i have had no difference in my discharge since the problem occurred. Thank you!