Hello, since Bilastine is a newer drug its safety in pregnancy is still not understood clearly. The drugs safe in pregnancy are Levocetrizine, Cetrizine and Loratidine. However if you find cetrizine ineffective, you may consider strating Fluticasone nasal spray which is quite effective and safe in pregnancy. And regarding Montelukast, it is usually preferred for asthmatic patients.
Next Steps
Start Fluticasone furoate nasal spray twice daily 2 puffs in each nostril and oral cetrizine at night
Health Tips
Avoid Bilastine and montelukast