It’s the most confusing part for the beginners to know if google analytics code is implemented correctly or if removed a duplicate script. One way is to open your code and search for the tracking id manually which is a daunting process.
Alternately you can install google tag assistant, extension for chrome which will indicate if the tracking code exists on your site. This will also indicate the issues which are causing problems in sending reports to analytics.
The last way you can check is by looking into real time reports in your analytics reporting section. If you don’t see any real time visitors, this may indicate some code implementing issues.