How long have you been on this dosage??? 20mg is very low. You may need to increase it to 40mg and give it a couple weeks. Typically you may have some side effects for a couple weeks after starting it and after each dosage increase.
over a year they helpd at 1st
Some people "poop out" on this and other medications after a period of time. The usual strategy is to increase dosage to 40mg for a couple weeks, and if needed, after two weeks, 60mg. If after two week at 60mg, you may talk to doctor about changing medications. This is a very common issue and will typically get better with either te increase or change to a similar med.