why do i feel tiredness in class?

While you're right that lethargy is a symptom of many types of diseases, because you only claim to feel it during this specific class, I doubt you're actually sick with any of them.  I think you're probably tired and bored in class because you find the class boring and tiring. 

Liking your teachers is not a requirement.  But paying attention and doing your best is.  I totally get not liking your teacher - I had an English teacher in high school (twice, unfortunately), who I couldn't stand.  I put up with her, though, because she was the only person teaching the specific class I wanted and needed for college.

If you're 13, you're either in junior high or high school, yes?  So I'm assuming you only have this teacher for one class out of the day.  If you really don't like him, you could try going to your guidance counselor and explaining that his method of teacheing isn't working for you, and you'd like to know if you can switch to a different class/teacher for that period.  It might not be possible, based on the class and the school's schedule, but if it is, it's not too late in the year to try.  Just be sure you have concrete reasons why you want to switch: "I don't like him" isn't going to cut it.  "He lectures too much, and I've found I learn best by DOING rather than just LISTENING" is a good reason - something that shows you've put some thought into it.

Worst case, you're stuck in that class with that teacher for the rest of the year.  The only thing you can do is to make the best of it - which I realize is about the worst advice you can get, and I'm sorry.  Throw in all the old cliches: life isn't fair, lemonade out of lemons, uphill barefoot in the snow both ways, etc etc.  Try to find something to get you through each clas that won't get you into trouble, do your best, and if you ned to: ask for help so you can actually learn what he's trying to teach you.

Good luck!