how do i get the groups which i have joined
There is a view that comes with OG 7.x-1.x (I'm using 7.x-1.4) that displays all of the groups subscribed to. If you have views running, you could  simply append /user-groups to your url and you should see it. After that, you can go into the view and modify it to meet your specific needs (e.g., make a block or whatever).