Took 1 dose of xyzal (levocetirizine) and i woke up had difficulty breathing and dizzyness until now. is it some side effects? or am i paranoid?

Xyzal (levocetirizine): Has sedative side effects and you may wake up dizzy and tired from it, but not necessarily out of breath. Try taking half a tablet until you get used to its side effects then you can titrate up to a full pill.

Likely side effects: If a drug has caused you side effects and there are other options, i would try the other drugs instead. There is no good reason to stay with xyzal (levocetirizine) at this time. If you only drowsiness, i would think halving the dose may be an option but it is only prudent to try another preparation because of the shortness of breath issue.