Finding out your whole life has been built on a lie is devastating and I’m sorry you’re going through this. Your mom probably thought she was protecting you, but lies don’t protect people, they just delay the pain and make it worse when the truth comes out. You deserved to know the truth from the beginning.
You have every right to be angry with your mom right now. She made a choice to deceive you for years and that’s a breach of trust that’s going to take a long time to repair, if it ever can be. Don’t let anyone tell you to “get over it” or “she did it out of love.” Good intentions don’t erase bad actions.
The question is, do you want to find your biological father? That’s a deeply personal decision and there’s no wrong answer. Maybe you need to know where you came from and maybe you don’t want anything to do with a man who wasn’t there. Either choice is valid.
Whatever you decide, please get some support. This is the kind of thing that can really mess with your sense of identity. A therapist can help you process all the feelings that are probably flooding you right now. And take your time. You don’t have to figure everything out today.