Sick as a dog :O(

So, my boyfriends kids (10 & 5)come over and stay with us 3 days a week. They're constantly sick! Very picky eaters, and BF lets them go to bed late... So they're immune system, as you can imagine, isn't the strongest. Everyone refuses to get the flu shot, only I've received it. EACH child has been sick 3 times since October- and I've held out strong- until now! I am sick sick sick & so miserable! 
How do I address this issue without causing turmoil between boyfriend & I? I don't want to seclude myself from them but at this point if he doesn't even enforce washing hands after the bathroom, I feel like I'm going to have to not touch anyone and stay 3 feet away. 
Am I overreacting? What can I take medicine wise? Headache, sore throat, congestion in chest. FTM 7 months pregnant. 
Rant over, thanks in advance.