Is is possible to get a false positive?

I took 3 pregnancy test and the positive sign was very faint but I'm sure it was there, but I don't feel pregnant. I feel normal. I do have slight nausea, and I am a bit moody lately, but other than that nothing really big has changed. My boobs don't hurt, I'm not any more tired than I usually am. My first doctor's appointment is soon and I'm worried/scared that there won't be a baby inside me. ?