Fertility treatments

Me & my husband have been trying to have another baby for going on 4 years now! We have had no luck , I've been on 2 different types of prenatal vitamins for a year now (my doctor says prenatal vitamins work for most women to get pregnant) Does anyone have any advice for me? Has anyone had fertility treatments? What kind was it & how long did it take you to get pregnant? Or is there any other way to get pregnant have I haven't tried? I need some help please!!