I love my girlfriend sexually but do not want penetrative intercourse.

I have been going out with my girlfriend for almost seven months now and we're very close. However she's been growing increasingly frustrated by the fact that we have never had sex. Truth be told, I've never had sex in my lifetime nor do I want to. Nothing about intercourse attracts me and, in fact, nothing could be more of a turn off.

It's not a matter of impotence or asexuality or anything. I can masturbate normally and am certainly aroused by my partner but, whenever we attempt intercourse, everything falls apart. This has prevented me from having lasting relationships in the past and I genuinely don't want to lose her. I've tried bringing myself to have sex but I just find the entire ordeal frankly painful and uncomfortable. It's not just irrational fear either, it's actually physically displeasing for me. To the point where I'm beginning to wonder if its less of a mental block and actually something physical instead.

Hence why I'm asking, is this normal? And is there anything I can do? My girlfriend has been incredibly patient and has not openly complained but I can tell it's bothering her and feel its incredibly unfair of me to put her through this.

Please help.