How many posts have I edited so far?
Can We check how many questions & answers are edited by own?
If yes then how can i check it?
One option is to see the edit count from "Editors" tab. First click on "Users" button on the top and then click on "Editors" tab. Enter in your name/ID in the box provided next to "Type to find users" label. Number of edits will be displayed below the reputation points and badges. I am not sure but I think this count is a total of text edits as well as re-tags that you may have done.
Second option is to execute the following query on data.stackexchange.com but that will not give you the latest count as the data is dumped every month:
SELECT COUNT(DISTINCT RevisionGUID) FROM PostHistory WHERE UserId = <YourUserId> AND PostHistoryTypeId IN (4,5) -- 4 and 5 are post title and post body
Third option has a number of links to click. Find a post that you may have edited earlier. It shows "edited" label and then a date which is a link. Click on that link, next page with show you a complete change history. On the right side of each revision, there will be a "suggested" link. Click on that link and on the resulting page go to the very bottom. Under "Editor Stats" you will see a count of approved and declined suggested edits.