Should I tell that girl he’s cheating on her too?

It’s been more than a year since I reconnected with my childhood friend. I was happily single, but after I had a bad accident, he was there for me during that tough time. While chatting on Instagram and WhatsApp, we developed feelings for each other, and he confessed that he loves me. We eventually became physically involved. Everything was going well, but he started hiding a lot of things from me, like secretly meeting female friends from college and school, and taking weird pictures with them. Later, he told me that if I wanted to be in a relationship with him and marry him, I needed to lose weight, focus on my career, and get a good-paying job. I did everything for him, but suddenly, he started avoiding my calls and messages. I found out he was in a hotel room with someone else, and his excuse was that he found a better girl—she’s slimmer and a dancer. He blocked me after that. A month later, he called to apologize, but after 3-4 days, he did the same thing again. Now, it seems he’s doing the same to another girl he’s dating. What should I do? Should I tell that girl he’s cheating on her too?