Thanks, everyone, for the helpful replies.

I did read the whole thread, as well as several others. But, partly because you did not address that particular plagiarism checker, I'm just clinging on to a hope that it is not an absolute certainty that my essay will be detected by my university's plagiarism software -- an essay that I worked hard on and that I foolishly put through that ******* plagiarism checker.
So, WB, thanks a lot for the comments. Although their content is negative and deconstructive, they are actually very helpful as deterrents. But some positive and constructive content would also be helpful; ie. what to do, as opposed to what
not to do.
What do you and the other writers on here suppose that I do with my paper now? Should I just throw it in the trash, delete it? Should I start all over again? Is it an absolute certainty that my essay will be detected as plagiarized (even though it is 100 % my own, of course)?
PS. My paper is due in a month. Should I go to my lecturer and tell him that I used a plagiarism checker on a site that sells essays?
Also, I will go to my lecturer and tell him that I used a plagiarism checker on a site that sells essays, which is the truth. It's a really, really important paper. Wow, I don't feel great about this. I hope he understands.
Btw, does anyone have alternatives? Going to my lecturer seems like the best option, however I am open to suggestions.
On a completely different note, ESL writing seems to be a huge issue in your business. There is some funny stuff on this forum about Kenyan and Pakistani writers. I can only imagine how much excruciatingly bad ESL writing there is. But, as you will know, there are always exceptions to the general rule. I am one such exception. English is my 3rd language. In spite of that fact I am completely fluent. Yes, I ****ed up and yes I'm on a tight schedule and need help, but I am an outstanding writer with lots of substance. My lecturer actually suggested that I revise my last paper and submit it to an international peer-reviewed academic journal. ESL writing is usually garbage, though. So many retards around.