What could it be?

My baby father and I have been together for 2 years and we're expecting our 2nd baby in April. But the thing is, he has been cheating on me with his 1st baby mom this entire time. She use to post videos of him online, or she'll tell Facebook she loves MY man And their child while laughing at me. He would neglect our bills just to get her food or $400-500 for their child. Then she'll post 3-10 guy's driving her and their child around to the park, out to eat etc. Then she'll go back to posting videos of MY MAN hugging him with their child at The park. Etc kissing on him. Like last month, he left me at our house with our toddler all night (8pm-5am). I think he was with her. Which she said online, "You're just mad because every guy wants me including your man". Along with, "I gave oral to another man and the next day, Your man bought me food". I just don't like the fact my man is always talking about her. She just put a PPO on him and he's still MENTIONING HER EVERY SINGLE DAY! Like what is it about her that he won't worry about me instead of her ..She's a SLUT! 😤