Safari will not retain history or cookies

Currently am running El Capitain (10.11) and Safari 9.0 on late 2012 vintage 15" retina macbook pro. Two days ago, for some reason, Safari stopped remembering new cookies and new history, as if stuck in private viewing mode. Did not change any preferences and can't restore Safari to its normal function. Tried erasing existing cookies and history and clearing application caches but it still will not remember any new additions. Very difficult to use as no sites remember me and I must re-authenticate. Currently locked out of several sites. Safari seems to be behaving strangely in other ways - won't let me fill out forms in some sites. For posting this message have to use Firefox. Any help would be appreciated because functionality of my mac is severely compromised.