Getting over him

What do y’all do to get over your ex? Especially when you two have a son together, a son who he rarely ever sees. I feel that’s what makes it harder, the fact we have a 5 month old together and he never sees him. Last time we broke up, he had hickeys. So I know he’s fooling around 😪 how do I get over it. Get over him. It was one sided lately, I felt I was the only one who wanted this relationship. I finally give up. I just don’t know what’s next. I’m only 20. So, raising my boy on my own is tough.