You can log in to your account by clicking "Log In" on the Libraries' website, then selecting "Dashboard" under "My Account."
Under "My Checkouts," you will see a list of any items you currently have checked out.
If you see an item under "My Checkouts" that you believe you have returned, please see this FAQ for "What should I do if a book is still on my account but I think I returned it" for further steps. Please note that it can take time for an item to be checked in after you have returned it.