Dienogest is usually recommended in women with endometriosis who have symptoms like painful periods, painful sex, heavy periods etc. It is to be taken in a dose of 2-4mg daily. It gives relief from the symptoms and also decreases the endometriosis lesions thus improving your chance of conception after stopping it.
Next Steps
Since you are 31 yrs and have been already trying for an year, it would be ideal to get onto Ovulation Induction medication (with preferably IUI) to up your chances of conception.
Health Tips
Speak to your doctor as to how long she would want you to take Dienogest and then get onto fertility treatment as early as possible.