Iam 35 Years And Am Trying To Conceive. I Weigh

Iam 35 years and am trying to conceive. I weigh 60kgs. I have a boy aged 8years and i had a coil for close to 8 years. I removed the coil early this year but and have been monitoring my ovulation days, taken fertility tabs , gone to scan just to be sure the egg is available and get to have sex after but still havent been able to conceive. Have tried for the last three months and nothing is happening. What could be the problem with me? thanks alot