Please help! account blocked, even after code acceptance and new password

I keep getting a notice of unusual activity, so I followed directions and got the new code and changed the password. Good, all done, it all works. Then I was working on an email, go to send it and it won't send! Unusual activity again, but this time when I follow the link it doesn't pop up the page where I ask for another code. I am receiving emails from clients but it will not let me send anything out. I went thru and changed the password again, but still it will not send out my emails. Please help!