You should review your credit reports (free from the site below) for inaccuracies and indicia of fraud.

https://www.annualcreditreport.com/index.action

There are multiple high and low risk factors due to which the score keeps on fluctuating. You can do a selfy analysis with this article https://turbo.intuit.com/blog/credit-score/why-did-my-credit-score-drop-2949/