1. It all depends on how long have you been taking the medicine and how much your acne has reduced
2. If you have joint pains it could be due to the side effect of the medicine but if you are having good improvement in your skin problem it will be inadvisable to stop the medication without the advice of the dermatologist
you have to weigh the pros and cons
3. It is better to get a liver function test and lipid profile done if you have been taking for more than 3 months.