Will This Change Things?

I have recently started sucking off my best friend since childhood but it's not romantic he asked as a favor and I am not sure how I feel about it but did it for him 3 times in the last two weeks.

I am a virgin and he is not. I am a bigger girl and not that attractive and never had a boyfriend. He is average I guess and has had several girlfriends and has one now. We are in the same friends group but he and I have always been best friends since our houses were across the street all our lives. It's always been platonic and aside from joking around never romantic... I mean I never had those feelings.

He has a girlfriend who he is fucking and she is very pretty but he says she won't suck dick. I know because we tell each other everything. So, he just straight out asked if I'd do that part without telling anyone. At first I tried to back out saying I was a a virgin and didn't know how which is true. Also we are best friends so this is weird. But he just pulled it out in my room, after school, and started stroking it right in front of me without saying anything more. Ahhh... it was the first real dick I had seen and I couldn't look away.

It was so hard so fast. He sat on my bed right fucking beside me ...stroking his incredible dick. He even pulled his balls out. Fuck. I was in shock but when he groaned in pleasure jerking his meat I felt it in my pussy I was getting wet. I may be a virgin but it's not by choice and I got so horny right away despite not having feelings that way for him. I was glued to watching my breathing got harder and he took my hand and put it on his shaft.
He guided my hand to stroke the full length but to slightly squeeze at his dick head ...he kept repositioning himself so that each stroke and dick head squeeze got closer and closer to my face. Soon I was beating off my friend right ... I felt the tip on my lips. He gently removed my hand from his dick and I felt him grasp the back of my hair. And the next thrust I felt push on my mouth and I instinctively opened and he pushed on the back of my head and I had a mouth full of cock.
Thankfully he I didn't gag because he limited how much went in. At first he just kept it there in my mouth. I didn't know what to do next. He whispered my name and I looked up with his dick still in my mouth. He was smiling so big and happy and mouthed the words "Thank you" but didn't say it... just mouthed it.
The he used my hair to pull my mouth up and down his shaft over and over as he match his thrusting... he told me when loosen my mouth because of teeth and how to tighten my lips and tongue at the dick head at the end of a stroke untill he plunged my head back down his shaft to the base over again.
Soon his was moaning so hard and started tell me I was making need to cum. I didn't know what to do but he had me by the hair (it was not rough nor hurt but he just kept control) he started going faster and it was very hard not to gag then suddenly he pulled out of my mouth and cum was shooting out of him all over my chin and neck.
He was apologetic for cumming on my face like that I told him it was fine and I thought that was normal from the porn I watched.

The second and third time I did it he encouraged me play with my pussy and make myself orgasm while we do it. He said it was only fair I cum too. He says to just relax and concentrate on my pussy and organizing and he will use the back of my head and hair to do all the pacing at his end. Both times I had earth shattering orgasms with him that way... him using my mouth like that while i rub my button and finger myself....fuckkkkkkk yes!!

I asked if he wanted to fuck me because I am still a virgin at 18 and have a low chance of a boyfriend but he says he has a girlfriend for that and that is a step too emotional for friends to go.

We don't kiss, cuddle, or act different at all. But when we are certain we are alone I suck his dick and he dirty talks me to an orgasm and afterwards we don't talk about it. We have talked and he wants to keep doing this until we graduate and go to college next year as long as I swear to not tell anyone.

Ok. I know I am being used and by my best friend. And even if there are no romance here.... fuck I love being cummed on and him seeing me orgasm. I also feel bad for his girlfriend who is really nice to me. Yet I really want to literally fuck her man but he is very clear he will never do that. He says it will change things. I won't... I am horny not in love. I think he won't because I am fat and not good looking but she is like so pretty.

Will this change things. What should I do?