You need to realise that a lot of woman specially once out of there teens have a lower sex drive if she feels your wanting sex every time then she is going to go off wanting any kind of sexual contact.
Just be close to her the weekend don't try to kiss when her step bro is there unless she kisses you then just give her a kiss back. You need to understand that it could also be a fact that your girlfriend feels that you only want her to come over to have sex every time and that's another reason she is going off sex now.
Just let things develop naturally between you and if you have to masturbate a couple times before you pick her up so there is less chance of you getting aroused when your with her.
The time will be right when and only when she decides no one will be able to tell you when she is going to want to do anything sexual, you can still take her back to your apartment but do something else like watch a movie on tv. You say you can control yourself but then you say you need some sort of sex with her well to me that isn't being in control! If you keep feeling the need to have sex every time your with her then masturbate more until that feeling goes away. Find out what she would like to do at the weekend when you talk to her on the phone the when the weekend comes make that time you have together special and as I have said don't pressure her an make feel she has to have sexual contact most woman are just as happy to go look round the shops or go for a nice walk in the park.
There are less woman around that have a real high sexy drive compared to males especially makes in there mid teens to late twenties, there is no real true figures for how many woman masturbate but the range statistics show in from 17.9% to 92.6% so as you can see it's something that can't be answered.
Most woman will try it at least once as to wether your girlfriend does I don't know as for her being frustrated she may just have a low sex drive and any needs she does get she overcomes.
As I have told you before there is more to a relationship than just sex and he your girlfriend feels like she is being pressured for sex every time she comes over then your just going to push her away and eventually your loose her you have already had her bring her step brother and I would say that was a big sign that by doing that she knew nothing sexual could happen.
My advice to you is if you want to keep her then just be patient doesn't matter how long it takes and when she feels ready she will let you know other wise if you feel you can't wait then you need to let her go and find another woman who can for fill your needs, any woman will get bored of constant sex though after a while if they feel that's all a relationship is based on.
Just because you see in porn movies about woman craving sex 24/7 it's not like that in real life.
You say your patient with her and do other things them in the same conversation you start on about having sex with her and wanting kids in the near future, STOP THINKING ABOUT WHAT YOU WANT! Your girlfriend is an independent woman and would probably like a career he she has been studying at collage before she settles down, to me you maybe in your country you dominated woman in past generations but that's not how it is now woman are independent and don't want that now, if you don't stop just thinking about what you want all the time your going to loose her.
Blankcanvas has given you a lot of good advice that you can't seem to take in and understand so if you want to keep her do what he says!
You say your patient with her and do other things them in the same conversation you start on about feeling like your running out of time and having sex with her and wanting kids in the near future, why do you want do you want all this so fast if your only 19 because he your right together you have a lifetime, sex isn't just intercourse it can be anything that leads to intercourse ie kissing massage hugging her because in other posts you have made you say you find it hard to hold back and get carried away, STOP THINKING ABOUT WHAT YOU WANT ALL THE TIME! Your girlfriend is an independent woman and would probably like a career he she has been studying at collage before she settles down, to me you maybe in your country you dominated woman in past generations but that's not how it is now woman are independent and don't want that now, if you don't stop just thinking about what you want all the time your going to loose her.
Blankcanvas has given you a lot of good advice that you can't seem to take in and understand so if you want to keep her do what he says!
I think you are not going to get any nooky BIG boy and it serves you right for having such a big tool, I am so glad I saw this because I have always been considered smallish just over six and a half on the horn but pretty thick and able to satisfy all the girls I have been with, better get those fingers working and maybe a fake p***y from the sex shop.