Help! 😡Need advice on how to deal with my boss

My boss has been incredibly sick with a nasty cough and congestion for THREE weeks now. Last week, I was off because I had caught something and I come back in this morning to find out she hasn't even been to the doctors to see what she has which I'm thinking could possibly be WHOOPING COUGH!
I feel she is being totally irresponsible and incredibly selfish and she should work from home until she is better. 
I don't want to tell her I'm pregnant as I have the opportunity for a pay rise and work from home options at the end of next month. 
I just need her to understand the severity and risk she is putting us all under. 
I don't know what to do or how to bring this up with her. I'm so upset at the thought of being as sick as I was last week again and what implications that must have on my baby. 
If anyone has any advice on how to deal with this, I would be so grateful.