I Woke Up To My Carbon Monoxide Alarm Going Off

I woke up to my carbon monoxide alarm going off at 12:05am. So just 4 hours ago. I woke up as soon as it started and realized someone left the oven on. I opened all of the windows and checked on everyone whom is still sleep. I'm a hypochondriac, and I looked up things on the Internet that now have me concerned. I have a slight, faint headache, but I also had a headache before I went to sleep. Am I being an overreacting hypochondriac or was opening the windows not enough?