Thanks for giving us more background info, logon82. Perhaps you should talk to him, especially if work is legitimately stressful. First, approach him in a teasing manner. Playfully offer to help him relieve the stress (it helps if you’ve already begun to set the mood with low lighting, music, and lingerie). If that doesn’t work, then have a serious conversation about the issue.
Above all, make sure that he isn’t just making excuses. If he keeps giving more of the same lines, such as, “Family problems are stressful” or “Mowing the lawn is stressful”, then he may be avoiding sex. I am not trying to make light of his problem if he really is under a lot of pressure at work, but when men say, “Work is stressful”, it’s often the man’s version of “Not tonight, I have a headache.”
Best of luck to you. You are young and you should be having as much sex as you want, especially if you’re in a relationship.