What should I do in this relationship?

I am a 23 year old male and I have been in a relationship for 7 months and recently I have found myself not wanting to be around my partner. There are numerous factors that I have identified as being the source of my issues. Firstly, I am working a job I absolutely despise to be able to make a living. I work on average 55hrs a week (mostly night shifts) and don't get much time for anything else but work. Any time off work is usually spent with my partner in the house doing the same things. Secondly, our sex life lately doesn't feel as exciting as it used to be. My partner seems to require constant affection and always feels as though things must be sexual when we are in bed. The downside to this is that his performance is not the longest I've seen... often times I am left dissatisfied. I go through periods of where I am totally content with the relationship and could see it being something very long term to just wanting to periods of not wanting to be in a relationship. He is a really nice guy and treats me better than anyone ever has. I am unsure what I should do. It seems as though work and not having personal time is the major issue here but what is the best route for addressing the issues discussed. Is it that this relationship has reached its terminal point and we should part ways or am I just looking for the easy way out as we all do... Any personal experience would be appreciated. If you are here to complain please don't waste the time to post a response.