Headers already sent

Hi guys, my first post here so I’ll try to be brief.

Starting from around yesterday, I’ve been getting these weird errors when I try to logout, or post something new (I can post, but the auto save draft will give me an error)

The typical error is Warning: Cannot modify header information - headers already sent by (output started at /home/omg/public_html/lol/wp-includes/widgets.php:1559) in /home/omg/public_html/lol/wp-includes/pluggable.php on line 694

I don’t think I installed anything new…well I did, adsense manager and wp-polls..but it worked fine with wp-polls, I can’t disable a plugin because it will give me that error, also when I logout it will give that same error but on many lines, not just 694.

Any specific thing that I’m doing wrong?

Thanks for reading.

Edit: Oh also I activated WP-Polls widget. I noticed the error said something about widgets.php ??

Edit2: This is the error I get when posting something new, you know how it goes to save a draft automatically, it comes up with a red box saying this

Warning: Cannot modify header information - headers already sent by (output started at /home/omg/public_html/lol/wp-includes/widgets.php:1559) in /home/omg/public_html/lol/wp-includes/classes.php on line 788

Edit3: Also the error even happens when I deactivate a plugin, it gives the error but it deactivates it. If I go to post something, it will post it but it still gives that error. Can’t logout of admin anyway, kinda annoying <.<

Thinking of doing a backup of the DB and reinstalling wordpress, but what if the problem is within the DB? is it?