Lexapro..if it doesn't work sometimes

I am on 10mg Lexapro a day for 4 months now for general/health anxiety. I had lots of the usual symptoms with light headedness and fuzzy head being the main symptom. Since starting Lexapro, I have had possibly 3 episodes of the fuzzy head/light headed symptom, today being one of them. I have noticed a pattern and it is usually when I get stressed about upcoming events. This coming week I have visitors arriving for a weeks holiday and I need to do lots in preparation for their visit.


I am curious to know if anyone ever has similar blips, where everything is going well then out of the blue someday or toward the end of a busy stressful day you feel like the Lexapro just hasnt done its job?

One more question if that's ok. Can anyone tell me if a medication like Lexapro wears off toward the end of its 24 hours.

Many thanks to you all in advance.