Hi!
No, I don't really think you're being all that selfish. We can't really love others if we don't love ourselves first.
It's actually fortunate for you that you've been exposed to all this already. That way, you know what you'd be getting into if you get involved in sex very early. I think that's the real problem surrounding you. It's not the babies really but the sex that your sisters got involved in very early in their lives. Having babies is a wonderful but difficult thing. It gets even more difficult if a person gets into it much too early.
Many people here say that babies are a blessing and yes, they are, definitely but one must respect babies enough not to just get into the brithing process without having prepared for it. Yes, young women will eventually cope with their pregnancies but wouldn't you much rather be the young girl that you really are instead of having to care about diapers, formula, baby clothes, etc?
What I suggest is that you go through your life like a little girl and not to try and be too mature too early by having sex early in the game. That just muddles up the situation. If you do allow a boyfriend that privilege, you then become somewhat unsure whether he's staying with you for the free sex or for you. Keep it clean, keep it simple.
If God blesses you with children, then that's something you should really embrace -- in the right time. Eventually, all the people who say that all they want from life is a career, success and no babies because of this and that reason will find themselves around 60-70 years old, alone and without people who could love them the way only children can. When my dad died at 72 years old, I was there with my two sisters and my mom. His friends who would've wanted to be there weren't because they had their own families. What would've happened to the man who was my father if he didn't have children? He would've died alone without anyone praying by his side, singing to him as he expired.
I love my father so much and I am so blessed to have my mother still around.
I think you'd eventually feel your life complete only when you've left a good brood of children behind who have been well taken care of by two parents who have showered them by love, understanding and sincerity.
Please take care of yourself.
Erick