I need you to read this very carefully. I have hooked up with many 19, 20, 21 yr olds.
One thing is very true and universal with all women. If you have sex with a woman EARLY in any type of relationship, she will walk away like it meant NOTHING to her. If you want to keep a girl, you have to mind fuvk her first.
But.....
If that's your goal.
18 yr old to 23 yr olds are CRAZY. They like you one day, like someone else the next.
Here is your mistake;
First, expecting anything more than a few weeks with a 19 yr old which you BUILT ZERO EMOTIONAL CONNECTION WITH.
Second, you saw her WAAAAAAAY too much. You can't see and have sex with a girl seven straight days and expect her not to get bored of you. See what happened? Instead of banging her for weeks, maybe months, you traded seven straight days for a fuvk buddy that could have lasted for months. You have to be unavailable, you have to treat her like crap, she is young, she wants what she can't have. You are old news. Just one more notch on her belt. You have to pretend, if not act, like you have TWENTY of her. You have to understand that she is young, and probably cannot be compatible with you in a relationship setting. You can't date this little girl. She is not a woman. All you can do is fuvk her till her eyes roll back, the way you do that is by establishing that she means nothing to you. TIME IS THE WAY TO A WOMAN'S HEART. NOT SEX. So next time, pull back a little, bang her but not for fuvking seven straight days. What's the matter with you? Don't you have a job? Studies? Or a family?
If a chick wanted to bang me for the third straight night, and she wasn't my wife, I would tell her that my covk hurts and that I need a couple days to rest from that mean ass puvsy of hers. I would also tell her that I have a family and I don't have time to fuvk her every night. I WOULD TELL HER SHE IS NOT MY GIRLFRIEND SO SHE DOESN"T DESERVE MY COVK EVERY NIGHT. Some guys will cringe at this, they will say "Dude, if she wants to fuvk, fuvk her, why you being a pusvy?" What they don't understand is that REJECTION keeps her wanting more NOT AVAILABILTY.
LEARN FROM THIS.