Like they said, if you have sex, no matter what you use or do, pregnancy can always happen. When people have sex, some don't realize the consequences that can happen. All they care or think "it's fun and harmless, i'll never get pregnant if i'm safe about it". Which is total bs.
If you are mature enough to have sex, then you should be mature enough to handle the responsibilities a child brings to you without thinking of abortion. If you're not ready to have a child, don't have sex.
If you and your gf is going to have sex, do everything you listed and have your gf get on birth control to help reduce the chances even more. If you are both teens, she can go to a planned parenthood and get birth control for free without her parents ever knowing.
But I must say this, when pulling out with the condom on,
hold onto the base of the condom. Wrap your hand around it or something. Holding onto it will help semen not spill out. Just be very careful with condoms as they can break and you never know when they will.