Part of it is time, it's not easy when you've been with this person almost daily for so long. Part of it is fear of the what if (she's been asking what I want-like do I want to be alone and will that make ME happy which from last time sucked so back we came back together a week later)-so i'm trying to make sure I squelch any doubt at all personally before I initiate actions I can't reverse.
A week alone?? That is nothing. OF course you will miss each other if you separate for a week. Your routine is broken, the silence in the house is deafening, there will be a huge void in your life. Have you heard the adage that it takes 30 days to change a habit? In some ways your relationship has become a habit. You've gotten used to the little rituals between you -- picking up ice cream, cuddling on the couch, talking about your days together, etc. And there will be a sense of grief and loss that goes with a breakup. Thus far you've both been envisioning a future together, a continuation of what you have now. So there's a sense of loss there when you have to let go of your vision of life together. All of this is undoubtedly painful.
But - it's also temporary. The pain of a breakup is intense but trust me, it is MUCH less painful to go through a short term loss than it is to go through a lifetime with someone who is not a good fit for you. It's not healthy to be going through the struggle you're going through right now. This is NOT a healthy relationship because fundamental aspects of it are mismatched. Come on, she wants marriage and kids right now, and she isn't interested in sex. You want sex, and aren't interested in kids or marriage. Wanting / needing sex isn't something you can control. As others have said, unless you're willing to sign up for a lifetime (if that's what marriage means to her) of sexless marriage, then you are being totally unfair to her by stringing her along like this. There is nothing to gain by waiting it out.
As others have also said, codependency really clogs up your vision. There is no way for you to wait out this birth control thing and have a clear view on what's happening. From what you've said here you are both afraid of being alone, so it seems like you will always be reaching for an excuse to make these issues a future problem to solve. It seems like BC is one of these convenient excuses.
If you do break up now, she goes off BC, you regain your sense of selves by being alone for a significant amount of time, even start dating other people eventually, you will discover whether or not you are right for one another (i.e. that her libido comes back, and you want marriage and kids.) There is no way to make these decisions clearly when you are bogged down in the mire of codependency.
So mind if I ask you what wasn't working in your relationship?
We were extremely codependent for one -- I have just learned from that time that codependent relationships are really unhealthy. We were both manipulative. We argued a lot (alongside a lot of really great times, too). It was intense and we thought that meant we were in love. I thought I couldn't live without him. We were both incredibly insecure. That sort of insecurity damages a relationship. I had to mature and be alone for a while in order to be in a healthy relationship, or even know what that was.
Basically I learned (just through figuring out what NOT to do) that while love takes
some effort and communication, it shouldn't be a struggle. I have never had a second of doubt that my husband was the right one for me. We just never struggled with the sort of questions you're struggling with (should we get married? should we be together?) We just knew, from the start, and still know. We don't manipulate each other to get what we want. We aren't codependent - we are two separate individuals whose lives work well together. We are on the same page 90% of the time. When we're not, we have a lot of discussions, and we listen to each other. That sort of thing.