I don't know whether or not you two have access to a counselor, but this does sound like something that the two of you need to discuss with professional help. Clearly, you cannot go into a marriage with this big of a disconnect between your needs and desires, and her apparent lack of interest or desire. You two need to discuss it and not just between yourselves, but with someone helping who has seen this kind of thing before.
Hmm, so much unsaid. You have had full sex so this is not a virginity issue. Has she ever had an orgasm with you? Do you ever offer oral sex? Is it about fear of pregnancy, contraception, monthly cycle, gender identity? Does her choice of engineering tell you anything about her desire for relationships? Counseling will help answer these questions if she will go for it.
So, I can tell you as a woman a few things. When I was young and striving to get through college and start my career, one thing was for sure. Pregnancy would have derailed my dreams. I did not want to become pregnant. It would have been unacceptable. The only sure way to not become pregnant that is 100 percent guaranteed is to abstain from intercourse. Are you positive that she doesn't have this fear in the back of her mind? She very well may. She may be afraid of std's and all of that and feel safer doing what she is doing. You are not yet married. She may have some head games going on about the morality of it all. I don't know. But for the sake of any long term relationship, being open and talking about things is a good habit to get into. Have you asked her how she feels, why this is occurring and expressed that you'd like more actual sex than hand jobs?
Okay, this may be tough to hear, but maybe she doesn't like sex. Maybe she feels badly for doing it outside of marriage, maybe she had feelings about doing certain sexual activities, or maybe, just generally, she doesn't like it.
What precautions are you taking to prevent pregnancy? Is she on the birth control pill? Are you using condoms? If she is on the pill, that can affect her hormones and may be affecting her sex drive.
Is she on any other medications? Anti-depressants can affect the sex drive, too.
How does she seem with you at times you are not having sex? Does she seem interested? Happy? Like she enjoys your company?
She is not lazy. She just doesn't want to have sex.
I don't know if she isn't interested with you, or just in general. Stop asking her to do it, though. You know she doesn't want to, and asking her to is cruel. If she won't tell you why, then maybe she isn't the person for you.
Are you familiar with attachment theory? Maybe her primary attachment figure was unavailable as a child and as such she finds it difficult to form intimate relationships. Maybe she was sexually abused by a family member when young and flashbacks are occurring. What kind of relationships did her parents have with each other? Talk with her about such things.
I know that at your age sex is very important, but if you want the relationship to progress you should back off expectations of frequent intercourse and let her indicate when she is receptive. Btw, the twice a month pattern suggests she knows when her fertile days are and she is using this as a further means of contraception.
I think the comment "she's not lazy, she just doesn't want to have sex" is right. She is avoiding having sex, and even avoiding you touching her on the breast. She doesn't want to have sex. What you have to find out (without accusing or fighting) is whether this is the way she will always feel with you. Saying you're "fed up" won't get you the answer, it will just make her feel worse for avoiding sex. Asking if this is the way it is always going to be is a fair question, just ask it when you two are in the care of a counselor so it doesn't become an argument some night when you are wanting sex and she is not.
Hi, michbehi! Reading your post, I feel like you really love her. But the sex thing is the problem that needs to be solved, and it requires work from both of you (not just you). If she really loves you, she will not mind to go to a sexologist to find out what is happening. To save your relationships and your connection you shouldn't avoid the problem and the discussion. It is quite probable that she has another sexual constitution and needs little sex, but you should go to the specialist and know it for sure. If you are going to get married and you have such serious intensions, you should solve it ( and she shouldn't be so closed considering this issue, as this is important for you) .
Is there a chance she was sexually abused at some point in her life? The looking at the wall just seems to be a real sign of disconnecting from the emotional part of sex.