What's wrong with me

My husband and I have been trying to get pregnant for 2 years and nothing. My periods used to be really crazy.. One time I had it for a whole year. Then I went on birth control for 2 months to regulate everything but it made me feel like crap so I stopped. Now my periods come and go like normal, lasting no more then 7 days. I have also lost some weight. About 35 pounds. I am not over weight but I am a thick women. Didn't know if the weight is what helped my period. My obgyn told me I have a low sitting cervix. Does that hurts my chances? Also my older sister has only had 1 child and can't have more cause of PCOS. I don't think I have that and I come from a long line of women who can have multiple children. I know my husband sperm is good because his relationship before me he got her pregnant. So I know it's me. Can anyone help?