Have Small Penis Near Vaginal Entrance, Cramps. Family History Of Breast Cancer

Hello. I am 18 years old and I've had this problem for as long as I can remember. I'm not to comfortable letting doctors see it so I've asked my sister if it was normal and they said no. Okay, so... Here it is... I have this 'small penis' (that's what my sister called and its about the size of the a pinky from the tip to the first bend) like thing that my vaginal entrance and I'm starting to feel pressure down in that area. Also, I have terrible cramps unless on birth control and even before I started the birth control I was having this weird yellow icky discharge. I've never had sex and it is physically impossible for me to use a tampon due to the 'small penis'. I'm honestly really concerned and I don't know if the fact that my mother had breast cancer when she was carrying me, that both my parents were in their late 40's, or that my dad only had one testicle had to do anything with it. Please help. I'm really worried.