dear mr. li,
      i'm sorry to tell you that i'm not feeling well today. i've had a headache and a cough. i didn't sleep well last night. i went to see the doctor this morning. the doctor told me i had caught a cold, and i should stay in bed for two days. so i'm afraid i can't go to school today and tomorrow. i hope i'll be all right and go back to school the day after tomorrow. thank you.

敬爱的李老师：
    很遗憾地告诉您，我今天很难受。昨天晚上我又咳嗽，又头疼，一夜都没睡好。今天早晨我去了医院。医生说我患了感冒，并且应该卧床休息两天，所以恐怕今明两天不能去上学了。我希望我赶快好起来，后天到校上课。谢谢。

dear mr. li,
     i'm afraid i can't go to school today. i've had a headache and a cough. i didn't sleep well last night. this morning i felt even worse, so i had to go to the hospital. the doctor told me to have a good rest, or it would get serious. so i would like to stay in bed for two days. i hope i will get well and go back to school as soon as possible. thank you.

  敬爱的李老师：
    恐怕今天我不能去上学了。昨天晚上因为头疼，咳嗽，一直都没睡好觉。今天早晨更难受了，于是我不得不去了医院。医生让我好好休息，否则病情可能会加重，所以我想卧床休息两天。我希望我能尽早恢复健康回校上课。谢谢。