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.
Sincerecly yours
XXX
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.