The only way that you are going to make sure that there aren't any irregularities with your credit score is by checking it on a regular basis. This is a good practice to adopt because you can deal with any problems in a timely manner and not let them come to the surface when you are in need of urgent credit.
At a minimum you should check annually and unfortunately most people don't do this.
You should always check your credit score at all the main credit bureaus as some will have different information than others. If there is anything that shouldn't be on your report then let them know immediately and find out where the source of the problem is before it becomes a bigger concern.
Usually it will only be a mistake that the credit bureau has made and that is why it is essential that you check with all the major credit bureaus and not just one. It could be the one that you didn't check that had the error that will stop you from getting the credit you need when required.
If the 'error' turns out to be a problem with identity theft then you will need to contact all the credit bureaus and get help from their fraud department.
They will place an alert on your file that will let anyone who is seeking information of your credit score know that you have been a victim of fraud.
The alert will also tell you when a lender is looking at your file and if this is happening when you aren't requiring it for any financial transactions then it might be because the identity thief is trying to get money in your name.
Alerts usually last for between 90 and 180 days but this period can be extended if you ask for an extension of the time.
When a lender sees that the person trying to get the credit isn't you they will deny the application and often alert the authorities to the person trying to get the money.