this professor(who's not much older than me) used to always look at me like 80% of the time when he's lecturing+smile+crack jokes and look at me.he kept doing this for like 10weeks but last week he just sudenley stopped looking now he never looks at me at all,he's totally ignoring me like i don't exist but still choses me to do presentations even when i don't volounteer why did he do that?(the looking+the ignoring+asking me to do the presentations...)i dnt understand!!! (btw i'm a very hardworking student,i always do my job,i don't aaaaaaaaalways participate in class because i'm sometimes way too tired or just dnt think i have something very interesting to say but i always take notes and pay attention+in the last cession he looked at me i participated,we discussed stuff,he was smyling....that's what made me even more confused.i didn't do anything so he would suddenley ignore me this way)so why is he doing this,and how can i get his attention back?
PS:please dnt criticise,just help me with your answer.Thank you