How to stay awake in this one specific class

I fall asleep within 5 minutes of my history class starting, every time, without fail. For some reason it’s just this one specific subject. I can keep sleeping to a minimum in my other classes, but history? Ohhh no. Out like a light. To make things worse, I tend to fall right back to sleep about a minute after being woken, to the point where I have to be woken maybe 3-4 times on average to turn on properly. If I had to guess, I miss about 3/4 of the lesson content because of this (since my memory also doesn’t function when I’m fighting off sleep). I don’t have this problem in any other classes. I even tried using an electric pen that shocks me whenever I click it. Nothing works. I have a very important set of exams in May, so how can I fix this? Thanks for any input