Simply deleting the data marks the blocks as not used. There is no flagging for overwriting. The space just becomes available for use. It will eventually be overwritten when other data is written to the drive. The odds of writes destroying your data depend on how much free space you have, how big the write was, how many writes there are, how fragmented your drive is, etc. etc.
If you wrote a bunch of data to the drive after the deletion, then sorry, but the data is probably unrecoverable.
And yes, there are more secure ways to delete files that will destroy the data by intentionally writing garbage data over it. I'd recommend you hide your porn better next time.