baby suddenly won't nurse to sleep anymore

Samara
I have always nursed my little guy to sleep for every nap and for bedtime, unless it's daddy's turn and he walks him around. Suddenly now he wil just scream and cry and fight to get away if I try to nurse him to sleep 😥 I will walk him around and sometimes that works but for the last week this has been happening and usually he just won't nap now, he used to nap every two hours. Any pointers? He will be 6 months next week