Why isn't it happening this time?

Mandy

I have 2 sons ages 8 and 6 they were born when I was 25 and 27. 2 year's ago my husband and I decided we would like 1 more and every month I use my opk tests it shows a surge and then nothing for 2 years my other 2 came so easy without even trying really. What is going on? I don't want to sound ungrateful because I do have 2 wonderful, healthy,handsome little boys but I just really don't feel done having children but am i?