Facebook keeps sending stuff i didn't send!?

[819]

For some reason facebook has been sending advertisements from my chat and saying I have sent it when I haven't! One of them was a Verizon Iphone advertisement the next one was a are you this person in this video the next was an IQ test and I have to keep apologizing to my friends saying I have not sent that! Please help!
Thank you soooo much for your answers I did every single one of your answers and it worked! thank you sooo much!

[Flayo]

Scan your comouter with your anti virus and anti malware software in safe mode. Then when your system is clean, change your fb password.

[mikiy assefa]

try by changing your password. maybe your account 's been hacked!

[Cari]

your account has been hacked. first, scan your computer with anti-virus software. then change your facebook password. make it something COMPLETELY different from your last password so there's less of a chance your account will be hacked again. then if none of those things stop the random advertisements, delete your account and start over. good luck!