Doctor, We Have Been Trying To Conceive For The Past

Doctor, we have been trying to conceive for the past four years to no avail, I'm a female and my doctor gave me Clomid to take 4 days within my periods. How is this effective and won't my husband also need some supplements to take as well? We have two beautiful sons, 15 years and 9 years respectively. We want to have our last born baby ay but it's difficult, please advise, thank you