OP, you need more help then anyone on this site can give you.
You are obsessed with a woman that has told you she wants space. You won't give it to her, you send flowers, buy gifts, text her over and over again and when she (she also needs help) calls you because she wants a bit of slap and tickle, you rush on over without giving it one thought.
You're 20, please tell me you know how babies are made!
Sex = babies. Is that simple enough? If you have sex, especially unprotected sex, it can and will cause pregnancy. You're playing with fire, with a girl that's stringing you along.
Seriously, keep it in your pants, hope for the best this time, learn and move on, get psychiatric help and live your life.