I feel really sad for my daughter today. My ex who was her father for the past 4 years, who I…

I feel really sad for my daughter today. My ex who was her father for the past 4 years, who I genuinely thought was her father, turned out not to be. We took a paternity test last year because his mother was putting tons of pressure and she turned out not to be his and he just dropped out of her life. I know it was fucked up but I loved him and I really thought he was her dad. we had a very on and off relationship for about 2 years before she was conceived, but he's the only dad she knew. Now she asks me if she has a dad and I never know what to say.