Iphone backup trouble

I now have trouble with my iphone XR - syncronicing with Itunes. When I got the phone, I connected and transferred the old phone to the new one. No trouble... But since then - whenever I connect my phone to Itunes, I get the message "Welcome to your new Iphone - do you wanna install like a new phone or from an old". The problem is, that the last backup was in april (when I changed phones) - according to Itunes. But I have backed it up maybe 1 month ago. Now I´m a little concerned, that if I say yes to either of the above 2 choices - then I will loose all data from now and back to april.... Itunes is newest version

Can anybody help me?

Will I loose data (textmessages etc) if I say yes to "restore from old backup"?

What to do?