Is it safe to use medicine telfast fexofenadine and medicine lyrica (pregabalin) during pregnancy in week 34 ? what side effects

Speak to your OB/GYN: Both medications are rated by the FDA as Category C in pregnancy meaning that side effects cannot be ruled in human subjects. Personally, I wouldn't want my wife taking either of those medications during pregnancy if she could either avoid them for other approaches or alternative medications (which there would be very few indeed). Best person for further advice on this topic would be your OB/GYN.