I often drink tea.是对的.
often 一般用一般现在时,再说后一句drinking现在分词,表示进行时态,还缺一个系动词（就是be）,例如：I am drinking tea.中,am 就是系动词,系动词的形式根据人称、时态、单/复数的不同而变化,看你问的问题,应该是刚学,但am,is,are肯定是知道的.
如：I am a student.
You are a student.
He is a student.区别在于人称；
My father is a doctor.
My parents are all doctors.区别在于单、复数不同.