I want to cry but I can

So I'm pretty frustrated. No matter how upset I am, I just can't cry. I cry when I'm frustrated but never when I'm sad. It just doesn't work. For example, I watched a show called Banana Fish. If anyone has seen it you know how horrible the ending is. When I was done with it, I was an emotional wreck, which was fine with me because I typically don't feel any emotion for some reason. In fact it was quite refreshing to feel hurt like that. But I just couldn't cry. It was like I was crying internally but externally it wouldn't happen. It's not fair. I think a possible cause for why I can't cry is my childhood. Because I have ADHD I also used to have really bad emotional disregulation. I cried everyday over the smallest things. That of corse led to bullying but I think the worst part was how people tried to help me. Basically I was rewarded with two stickers a day if I didn't cry. So as a child, crying always meant bad. Could this be why I can't cry? If it is, is there a way I can cry again? I'm really frustrated by it.