May be you need to modify this code..
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
httpclient.execute(httppost);
cnt++;
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
Use of httpclient.execute() twice might be the possible reason for the data being inserted twice.
Modify your code like this..
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
// httpclient.execute(httppost);
cnt++;
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();