I am unsure what is wrong?

I started my period two weeks before my 10th birthday and they were heavy and painful but in the summer when i was 12 they stopped and after 4 months of not having any I began getting pains on my left hip down to my pubic bone, the pain got worse and worse until I was taken to the doctor where he arranged a blood test and ultrasound scan. My blood was fine, so during the ultrasound she could not find my left ovary so another nurse tried and also could not find it they told me it was possible i only had a right one. Once i got my results they told me I have small cysts and they would go if i lost weight as i am obese. I have tried and im getting there slowly only to realise if i do not have a left ovary why am i getting pain on my left side and not on my right which is the side they saw the ovarian cysts. I do not want to go back to the doctors as they will just tell me to lose weight. I am unsure what's wrong i was wondering if anyone had any idea as to what it could be