Boyfriend keeps texting a girl he slept with

Backstory:

So while we were broken up, my boyfriend had sex with this girl. I’m okay with it now, however she texts him all the time, even once she said she started feeling sick indicating she may be pregnant. He has only responded to the pregnancy message, but everything else he doesn’t respond to. She was not pregnant, however she still texts him. Am I wrong for telling him to block and delete her number? He feels that he shouldn’t because he doesn’t text her. Call it a woman’s intuition, but I call it bullshit, and I will not tolerate it. What do you guys think?