Satisfaction

So my girlfriend of over two year and I have had a rift between us for a bit and its not a fighting point or anything, but it really makes her sad and I do not know how to fix it.

To start off she and I live a couple of hours from eachother and because of money and scheduling we get to see eachother around one full day a week. We usually make love on this day and spend time together all day. This bring us to the issue. My girlfriend has been telling me for a couple months she is not sexually satified in the amount of sex we are having and it makes her feel unattractive.

My girlfriend and I have acknowledged that we have different sex drives but she still gets very depressed if we do not have sex on a saturday or if she wants to do it multiple times and I really am not in the mood. My girlfriend is the most beautiful, sexy, perfect woman in my eyes and I try to tell her as often as possible and make her feel so, but my drive for intercourse is not high.

I put most of my value in our relationship on the time we spend together and on having new experiemces or adventures together, I love her so much and while sex is intimate and wonderful, and I enjoy every time we have it, I just sometimes am not in the mood.

When we first started dating we were extremely sexually active, going at it any time we could, but since then I know my hormones have changed and I just dont have the same carnal need all the time.

What should I do? Any advice would be appreciated.