All your posts are still here. Nothing is erased.
We use the Google and Facebook systems to sign you in. Both systems give you a unique ID. In your case, when you signed out and signed back in, we see a completely different ID - you are a different new "Ketan". That's why you see just one post against your name. The old "Ketan" has a different Google ID.
Please make sure that when you signed out and signed back in, you signed in with the same email address as before. Many people...
more... have multiple email addresses on GMail for different purposes. A different email means a different account.
If such is not the case, then it might be a bug with Google, giving you 2 distinct IDs for the same email. Please let us know, and we'll manually merge both IDs.
In any case, all info is still here. So no harm is done. Thanks.