What's wrong with me, please help

I'm a guy, and I'm 23 years old. I'm one of those guys that isn't scared of much, and I do alot to prove it all the time. Mostly stupid things like skydiving and driving too fast. Well, that was until my stepbrother started having seizures. At first I just heard about them, but in the last month I've witnessed two of them and have assisted him during his tonic-clonic seizures. First of all, it kills me to watch him going through that and I feel really bad for him. Powerless to help. I've tried doing as much research as possible and I'm not really getting anywhere. I know my stepbrother has done drugs, and may still do them. I say this because I'm just trying to be honest. I'm afraid that that's what may have caused him to start having the seizures. And it scares me. Why, you ask? I lived in Myrtle Beach, SC for three months, and worked in a stripclub as a barback. I had alot of fun while I was there, which was just this year, but I also got irresponsible. I did cocaine and ecstasy, and drank alot. I never thought before that I did enough to hurt myself, but that was before I watched my stepbrother go through his seizures. Now I'm truely scared. I dont touch drugs, or have anything to do with them. After my DUI last week I dont drink. I can't sleep since I stopped drinking, and when I lay awake at night I wonder when I'm gonna start seizing, and if I can stop it. I get this feeling over my whole body that I cant really explain. It's like a rush of adrenaline, but different. Like my body is preparing for something. I lie awake afraid to sleep because dont want to drift into the seizures like my stepbrother does. I had a dream one night that I was having a seizure, and I couldn't breath, and I couldn't move, and I couldn't scream. It scares me to death. Now, today I got the same feeling as I was laying on the couch watching tv. It's like a rush of terror and anxiety that I can only stop by getting up, thinking of something else, breathing, and drinking a glass of water. It feels like it's going to overwhelm me. The only time I feel like this is when I'm relaxed and sleepy and thinking about it. Like right before I go to sleep. I know this is kind of selfish to ask for help when it's really my stepbrother that needs help...but do you think this might be the beginning of seizures, or do you think it's a psychiatric problem? Any help would be greatly appreciated, I am losing alot of sleep....and it's affecting me during the day.