[Veni Vidi Vici]

Like PSY said, try to go to every lecture from now on.

I know this may seem a bit weird but if you REALLY get sick in class then you should sort of embellish it to make sure your teacher takes notice and sees that you've been telling the truth. That threat your teacher gave you is probably because he doesn't think you're telling the truth yet. You have no idea how many 'I couldn't attend because I was sick' excuses he probably gets so if I were you I'd make sure he sees you nauseous/dizzy as well as take your medication right in front of him. Hopefully this serves as a 'I told you so' towards your teacher and helps him realize you were telling the truth all along.

I know that plan could seem sketchy but that is what I would do; you wouldn't be lying, you would just be making sure he noticed your condition. After all, this IS your college education we're talking about, and it's very important for your future....

All the best... Carpe Diem.