Is there a way to show only the post that I've written?
But it sounds like you want the ability to search them. For this, simply include
user:51325 in the search box.
51325, because that's the number that represents your Ask Ubuntu user account. (It appears in the address bar, when you visit your profile.)
If you search for just
user:51325, then you'll see all your questions and answers, listed together, as search results. But you ccan search within that, too. For example, currently the search query
user:51325 nvidia shows just these three results, as they're your posts where Nvidia is mentioned.
When a user's profile is viewed,
user:N appears in the search box (at the upper-right corner of the page) automatically, where
N is the number that represents that user. So the easiest way for you to search through your posts is probably to go to your profile, then type your query into the search box (without removing the text
user:51325 that's already there).
Please note that this shows only posts on the main Ask Ubuntu site. It does not include posts of yours on meta, because meta is treated as a separate site. To see those, start from your meta profile.