Virgin but have loose vagina

I'm a virgin, but when I finger myself, it feels empty sometimes. Like if I put my legs up, or put my butt in the air it feels like a cave. I'm going to be having sex for the first time soon, and I'm pretty insecure about this. I can make myself tight again by pushing out the air, but obviously that's not gonna be possible in the heat of the moment. Also I have never put anything more than my fingers inside of myself, but I can still fit three fingers in without any pain. Is this going to make sex unpleasurable for him because I am too lose? Is there anyway to prevent this?