Masturbation is very healthy and will make sex with a partner more enjoyable and safer because it is teaching you what is normal for your body, sexual response and letting you explore your sexuality. This means when you have sex you can better tell your partner how to stimulate you, this not only makes sex more enjoyable but also helps prevent pain and vaginal damage during penetration.
Masturbation cannot have any negative effect on your fertility, it's also beneficial in reducing stress during pregnancy, aiding to induce labour and easing labour pains so it's beneficial in childbirth.
No. Jerk away, you'll still get someone pregnant!