Welcome, and well done on being diet controlled.
Stress can increase blood glucose (BG) levels for sure, so can infection. Are we talking about fasting BGs, and have they been in the 5s for a long time and went up suddenly? It could be due to several factors and the key thing will be look for trends rather than individual results. I would say, if they are still up this high after another week, then make an appointment with your doctor or nurse to find out what's going on. And if you develop symptoms suggesting an infection then make an appointment straight away.
Have you made big changes in what you are eating recently?