Yes, you can still upload your own loan contract to an Active loan at any time before it expires. Navigate to the Loan Details page for your loan and click "Upload Custom Contract?" to select your file.
Note that uploading a loan contract is considered a Premium Feature. If you have not yet upgraded your loan to a Premium Loan, you will be asked to do so before proceeding to upload your file.
You can read more about uploading your own loan contract in our FAQ titled "Can I upload my own contract for a loan managed on Pigeon?" or send us a message if you have more questions.