Gay encounter mistake is ruining my mind?

i am a 100% straight man, i always knew i have been. but i went through a phase of curiosity. i was watching gay porn/reading stories, and was getting a kick out of it. i had never physically been attracted to a man but the thought of receiving/performing oral sex from a male was just intriguing. i was masturbating to gay porn, but was emotionally and physically being attracted to women. it had been a few months since i broke up with my ex girlfriend of whom i wasn't really attracted and i wasn't having much luck on the sexual/physical side of things. i had kissed girls etc at parties, but nothing was veering near a relationship. then the thought had come into one day, why not try something different out, i knew i was 100% straight but because of that i was refraining from acting out on this silly curiosity. one day i was driving back from giving my friends a lift to a place, and i gave it into it. i pulled into a lay by/dogging spot, and although i was nervous, i decided to get it over and done with, because i thought 'hey!, no-one's ever gonna know about this and it doesn't mean anything' a man approached me, who told me he loved sucking cock, so i offered if he would like to suck mine. he pulled down my trousers and started giving me a ********. i'm not gonna lie, it was a good one. we moved it into my car and he carried on doing it. because i was in the state of arousal, i was intrigued by his relatively large and thick penis, and tried sucking it myself. i didn't enjoy it, but i was something i had thought about. i let him continue giving me head and because i was caught up, i asked if he'd like to **** me. he asked if i was sure. he put a condom on, and placed it inside me. it hurt and i didn't enjoy it, so we stopped, he finished giving me head, i wanked him off till he finished and we went our separate ways. but since it has happened, i have always regretted it, and no matter what advice and what i do i can't put it behind me because it makes me feel so dirty knowing that i'm 100% straight. the bad thing comes to play, that around 2 weeks later, i had met up with a girl who i had always been vaguely interested in. we hung out and ended up kissing, little did i know before that she had liked me, and if had been a few weeks earlier, i would have avoided this encounter. we've been out for 4 months now and we are in love. i just couldn't hold what had happened secret and had to be honest and tell her about 2 months down the line. she understood and forgave me, and said if i thought you was gay, i wouldn't be with you. but there's something in my head, always making me think she would be curious of me. we both love each other to bits, but when you tell someone something like that, i know deep inside it's hard for her to believe i'd never do something like that again. we've know each other for a few years, so she's seen the relationships with women i have had etc, but i am her first and she's my third person. the other two girls ment nothing to me (one being my ex) but i am completely and utterly in love with her and am in the state of feeling like i want to spend my life with her because she has the qualities of a great person. but although neither of us can see it, i'm 18 and she's 16, so we never know, something might happen a while down the line, and she might not be the one. i might encounter other relationships, and get married to another person. i feel lucky that i have found someone so accepting of my mistake, but it haunts my head everyday. i can't do things like listen to hip-hop music or go anywhere without it creeping upon me. i don't know to just let the thought escape my mind. i'm worried that if i don't spend my life with her, would i be able to tell other women as clearly as i did to her or should i just be keeping it a secret. i have no problem with gay/bisexual people. i just can't turn back time and it's killing me inside.