http to https general settings problem

hello

I wanted to change my blog from http to secure https and so I installed the wordpress-https plug in.
Then I changed the http to https://mydomain.com/myblog as my URL and homepage in the blog’s general settings.
 Now I cannot log in to my wp-admin.

It says “Safari can’t open the page “https://mydomain.com/myblog/wp-login.php” because Safari can’t establish a secure connection to the server “mydomain.com”.
if I type http://mydomain.com, it shows the blog but the layout is messed up, and if I click on any of the pages it goes back to https and same message as before.
I tried deleting the wordpress-https plug in and adding “define(‘WPHTTPS_RESET’, true);” to my wp-config.php file but it still goes back to https and same message when I click on any page.

I realized I have messed up trying to do this without researching it first and I am lost now. I have searched for a solution on the forum but no joy.

I saw “you need to make sure that you have your own SSL certificate installed on your domain” – I don’t know if I have this and I guess this has something to do with it.

For now I would just like to go back to the previous stage of my blog on normal http and be able to work on it. I guess I need to change those general settings back but I don’t know how as I cannot log in and I didn’t see anything on the options-general.php or the theme’s functions.php or the .htaccess.

Please help!!!! Thanks!

yolanda