Advice for sick baby

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My 5.5 month old has had a cold turned croup for a while and hasn't slept well for a week. We bought a swing in hopes it can help him sleep. If he doesn't sleep he can't recover. But I am so worried sleeping with us or in the swing will undo all of the hard work we have put in to him sleeping well in his crib. Any suggestions or advice? He won't sleep in his crib while sick, he just screams.