Girlfriend let me fuck her ass for her first time having sex [MF]

I got a new girlfriend a few weeks ago after we met at my job. I'm a 26M and she's 23F and she had never done anything sexually before outside of playing with herself. I have a decent amount of experience but don't know everything, but I felt that I could help her figure out the things she liked. After a bit she came over to spend the night at my house once and we were getting a little frisky, she ended up giving me a blowjob. Gotta say, she did really well for her first time. The other day, she came over to my house again and things got frisky again, but she does also have some issues being naked around other people so I figured it would be slow going. That being said with the amount of sex talk we'd been having I expected we would probably fuck soon. I should mention I have an anal fetish, it just is a really nice feeling provided it doesn't hurt her and you don't need a condom. I mentioned this to her, and she has also said that she is down to try basically anything, the only way to find if she likes something or not is to do it. We were waiting for my roommate to leave so we could get to it and I brought it up that we could do it since it could be no condom and no pregnancy worries, kinda as a joke and she said "I mean it's an option."

Once my roommate finally left I stripped her naked, and her discomfort was apparent. She said that she has never been naked with someone since she was a child and it was something pretty messed up (not her being sexually abused though). She said that cleaning herself off with a shower though should help her feel more comfortable. I jumped in with her to get hard to reach places and I asked her "okay really, would you rather be pussy fucked or butt fucked today?" She said "hey we'll flip a coin and you call it, if it lands on what you say we'll butt fuck, and if it lands on what I say then we can butt fuck." Now this may have been a slip of the tongue that she said the same thing twice, but I said "you know it's really sounding like you want to be butt fucked!" And she said "sure!" I kid you not my knees almost buckled from how turned on I was.

We finished in the shower and I got her on her hands and knees on the bed and started licking her asshole. I could feel her shivering but I have a really short tongue so all I could really do was lick around the outside. Eventually I got a bottle of lube and pressed a finger into her ass. She was shaking the whole time from this new sensation, but found it seemed to trigger a pleasure reaction bending my fingers down towards her pussy. I inserted another finger, and she had actually thought I was putting my cock in since she couldn't see what I was doing. I thrust my fingers in and out and she kept trembling from the feeling. Eventually I felt she was ready, but unfortunately my cock had started going soft. After making out for a bit, I was harder, but still not hard enough to push into her asshole. Feeling defeated, I just asked if I could jerk off and cum over her ass. She said yes, but then as I was doing that, I got truly hard again. So, I lined back up with her ass, and pushed inside.

Holy fuck was it amazing and the gasp and shudder she made nearly caused me to cum right on the spot. But I knew that if delayed too much I would go soft again and probably not get hard for a long time. So I pushed all the way to the hilt, making sure she was okay, and thanking lube for being so magical. I started thrusting, a bit slow at first, but then, confident I wasn't hurting her, started ramping up faster and faster until I was slapping her ass cheeks with my hips. She said she's not very vocal, but I could see the range of sensations passing over her face and body as I kept fucking her. But because she had been edging me earlier, I knew this would likely be a short fuck. But on what a fuck it was, I'm fucking her ass at full tilt now, trying to bust before I run out of stamina. "Hey I'm about to cum." "Yeah?" "You want it in your ass?" "Is it going to leak out?" "Yeah" "Are you going to watch it leak out of me?" "You bet your sexy ass I am" "Please cum in my ass baby" and with that I can't hold back and slam my cum into her used asshole. I can't resist but do a few more small thrusts before pulling out and sure enough, a small trail of white is leaking down from her asshole. God I can't wait for next time.