OP, i feel so sorry for you.
At the very first hurdle of family life when your immune system has taken a hammering your husband really doesn't give a damn about you and the baby.
40 people and their germs milling around your house?
Unbelievable.
What a shower you have married into.
Approaching 60 here and if you were my daughter I would be appalled with your husband and his family, and I would never forget this.
You need to leave that house for several days so that it can be thoroughly cleaned and aired before you return.
I really hope you are returning to work and have kept your finances separate.
I don't give your marriage 5 years.
His disregard for your health at this time is too profound a statement.
For his family to be so cavalier with your health and wishes is extraordinary.
For him to agree to this behind your back is such a betrayal.
Listen to your sister.
Keep your family close to you.
Don't protect your friends and family from the truth of who he and his family are.
Keep your health as your priority.
Your baby is going to need their one decent parent well.
After the baby arrives, going to visit and be looked after by your parents would be an excellent idea, now that you know he cannot be trusted to care for you as a priority.
Don't brush this under the carpet.
You need to be very wary going forward.