The doctor wants nothing to do with them lol
Need you also be reminded that he's currently the target of Reito's investigation pertaining to Lyca as well. They can't just go to him whenever they have a problem when they are trying to reconnect him with Lyca without him noticing.
And it isn't as simple as "Yoru feels sick." He's going into rut over a human which can lead to serious injury ((as we've seen)) if Reito shows any sign of rejection to Yoru's advances.
Lastly, we saw in the preview for 9.5 that Toudou purposely tells Reito something to make him believe that he isn't actually special to Yoru. He doesn't want them together 'cause all werewolves can do to a human partner is physically harm them in Toudou's mind. It's the reason why he ran away from Lyca in the first place.
Does that clear things up and answer all your questions lol
so the doctor is helping, this is nice it gives everyone a role in this story.