Carbon monoxide poisoning ??

So I live in Maryland and we just had a huge horrible snow storm with around 2 feet of snow. I've been hearing a lot of stories about people dying from carbon monoxide poisoning because their muffler was covered and blocked in snow and they sat in the car waiting for it to warm up. Well every time I go in my car I get really scared that it will happen to me. My boyfriend tells me to stop worrying because there's no snow blocking my muffler but I'm just scared somehow the carbon monoxide will get in the car because I use the heat on full blast. So today when I was driving home I tried to remember what my boyfriend told me and I tried not to worry but after about 20 mins in the car I suddenly got sooo sleepy to the point where I could barely open my eyes and that never happens to me. I even started getting a headache and feeling dizzy and I got so scared that it was carbon monoxide poisoning and I started panicking and drove as fast as I could. I feel a little better but I'm still soooo sleepy where it's hard to stay awake. Could it be carbon monoxide poisoning ?

Roll down or crack open the windows when driving

As crazyhazeynut mentioned - fresh air is the cure.

Wow I thought I was alone in this fear, I never even spoke about it to anyone. It's not about the car for me but my house for some reason, I recently had a detector installed in the apartment and my fears are gone.