Pregnant & Sick - Advice???

I'm 29wks along and a couple days ago I developed a cough. Since then it's gotten WAY worse (and alot harder when I cough) and I've started wheezing & coughing up bits of yellow mucus sometimes when I cough. My chest kinda feels tight too when I breathe & I have to take shorter breaths. My nose is stuffy & I can't really breathe out of it. I took my temp & it's only around 100F, but for me that's really high cause my avg normal temp is closer to 96F.

I'm worried because I'm afraid baby isn't getting enough oxygen cause I might not be, and when I called my OB they just said to take benadryl and some cough drops. I don't want anything to hurt my baby it even possibly go into preterm!!! O.O!!!!