tetracycline drug for perioral dermatitis?

i just 17 years old when i got this disease.  it is really painful. i cry every time i want to eat, brush my teeth, talk and even when i laughing. because my lip areas are so dry, tear. then, i just know that i have perioral dermatitis. before i see my dermatologist, i use vaselin to moisture my lip area. when i not apply vaselin, my lip area will be white color (soo dry ) but after i apply vaselin, my lip will be soo reddish(look like i having eczema)....doctor ask me to take tetracycline twice per day. but when i eat that, my lip become worsen. feeling like my lip burning all the time. am i should stop taking tetracycline or this is the real effect of this drug?please help me..i already suffer for 2 years. it really ruin my teenage life.....