Congestion and Sleep

Currently week 15 going 16. Was down with flu cough and fever during week 10 and after that all the way till now i have been having nose congestion and stuff nose almost the entire day and night. (Pregnancy rhinitis?) When its sleep time, I feel so stress that I am unable to breathe properly and causes me to be super fidgety and cant sleep every night. Gynae did prescribe allersin for me to take every night till no symptoms, but I am still congested.. I feel so helpless. When will this go away?