Why would my ex play such a mean prank?

So my ex and I broke up two months ago and I’ve had him blocked. He cheated on me and gave me a std he knew he had. I got tested and cured 3 months ago. While blocked I could see he called me many times and never got through. He was mostly calling me late at night. It’s been two months going on three at the time and I get a text from a fake number saying they got my test results at this clinic and to call or come in because of unfortunate results. I didn’t believe it cause I know doctors aren’t supposed to share that kind of information over text. As I’m texting the number he’s still acting like a doctor and telling me I need to come in cause my number is on file. After a few texts he admits it’s him.

Why would my ex play such a mean prank?
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