Night Terrors?

Andrew hasn't been sleeping so well the past few months. At first I thought it was just that he really needed a nap but the past week or two, he stopped sleeping through the night again... even though he gets a nap. When I explained this to a few people, they mentioned night terrors. Well I had no clue what that was and figured Andrew was probably too young to get something like that and so I brushed it off. But after doing a little research, I am beginning to wonder if he might be having these night terrors. He wakes up, usually around the same time each night, and screams his head off. No amount of comforting will help, in fact it usually makes it worse. He screams and screams and throws himself on the floor and I can't get him to orchestrate a real sentence to save my life. After about ten minutes of me just sitting there holding him and letting him go crazy, he mentions that he needs to go to the bathroom or wants a drink or last night he said he wanted to say a prayer. I feel like I am going to go insane. When I researched it, they said it might have to do with sleep deprivation but how can that be when he gets a nap? They also mentioned becoming aware of the need to go to the bathroom but it takes me ten minutes of screaming before he will finally let me take him. I don't know what I am going to do but if anyone has some advice on this subject, let me know. Maybe I will be calling the doctor this week. Another question... what am I supposed to do with Olivia? We are trying to get her to sleep through the night too but they just keep waking each other up!