Should I wait until marriage?

I'm an 18 year old male virgin, 19 by next March and so is my girlfriend. We have been together for 6 months now and have had sexual relations with each other, but never penis in vagina sex. At this point I really want to lose my virginity and stuff but I love my girlfriend by hurting her or something by leaving her. She was never really specific about waiting until marriage and it might be more about her fear of getting pregnant. I don't know what to do and I feel like a piece of shit for considering leaving her because of lack of sex.
Should I wait until marriage?
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