It stands to reason that you cannot fix a problem if you don't know it exists in the first place. So, you need to find out your credit score through a reliable source to determine how bad the damage is.
To run your credit for free, try first visiting Annual Credit Report.com. This site provides users with one free credit report every year to give you a decent picture of how you're registering on the credit scale.
The first is that you don't have enough credit. Much like the scenario we laid out above, if you are young and only have one credit card that you've maxed out, then it's likely that your available credit is low or non-existent.