Irregular periods. Me what to do?

My periods are irregular since 2 years. I have changed four gynaecologist and every time they gave medicine to come periods not to regulate that. In past I have two ectopic pregnancies. Now again I'm trying to conceive n not getting pregnant and still not getting my period on time. My all tests for this problem comes normal no hormonal imbalance no thyroid nothing but still my periods are not regular. And I don't understand why my doctors are not giving proper treatment to get my periods on time. My last doctor suggested me to took duphaston tab on every month on 14 days of my period for 10 days but when I stop taking this tablet I don't get my period. Plz suggest me what to do? It's been 3 years of my marriage and now I'm desperately trying for baby but nothing is going in my side. Plz plz help me what should I do. I am really very worried for that.