I am having a very similar problem. I am having not much trouble getting one night stands. Just 2 nights ago i f-closed an HB 9 with a killer body (she's a ballet instructor

) in 3 hours. Only during the morning after did i notice the picture of her and her boyfriend on her table. This is a girl I would have loved to have seen a lot more of and believe I could have had i not f-closed so soon. Dont get me wrong, sex with an HB9 can be fantastic and is something i could only dream of before starting this.
The point is that we both have the same issue. After talking on the site's chat some advice i was given was to not, under any circumstances, f-close straight away. It may even be a DHV if I do take this advice. I am going to try doing everything but se next time and then tell the girl how i feel she is too interesting to let one night determine our relationship. I may even say this after the number close and after the many IOIs (the obvious lets go back to my place IOIs). This will obviously take some work but i think to get past one night stands and onto relationships this is worth it. You can always split the week's scores between relationship material and one night stand material!! I know this is a long reply but i think its a question which seems simple but which is very complicated. Hope this helps and if anyone disagrees with me please let me know and i'll try something you suggest. Thanks!