Feel weird?!

I started working lately, im in college at the same time and i am often tired and stressed. My SO has been working for many years and now i can tell i understand him more. The problem is our sex life is awful. It doesnt happen as much anymore and i never finish. I feel unattractive although i feel loved. We are only 22 and together for one year and a half. I feel like being married?? Idk maybe its like this. What can i do?