Pete Davidson and his pregnant girlfriend, Elsie Hewitt , both say sparks flew fast ... so fast, she told him on their first date he’d be the father of her kids -- and he fully agreed.

The couple participated in a Q&A for Bumble on Wednesday, where they were asked, "When did you realize this could be something real?" Getty

Elsie says ... "When we went on our first date, like we went out to dinner for the first time, I was like, 'Don't think that I'm crazy, but I just know that you’re going to be the father of my children.’”

Pete felt the exact same way ... nodding his head, saying he responded, "I know."

Fast-forward to today, and the couple is now expecting their first child -- though the road hasn't been easy. Last week, Elsie revealed she’s been dealing with nonstop,

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