Telling everybody, 'Oh, my boyfriend and I went to ' is a no-no. It's ridiculous. You skipped work and now everybody, including your boss, knows it, because you actually told them.
The old-school rule was, go to work and let them send you home. I disagree. If you have an infectious disease, don't come to work and make everyone else sick. Call in sick, but do it courteously. No matter what.
Employers may not want to know the gory details of your illness. What we do want to know is if you'll be reporting for work tomorrow. You need to give an expectation of when you'll be back at work so your supervisor can arrange for someone to temporarily cover for you.