husband didn't interested in SEX!

Me and husband already married for almost four years. Both of us will be 30 next year. My problem is my husband always said he is too tired for sex. If I didn't flirt him, We can sleep without doing anything for 4-6months! I'm quite stress right now because I want to have babies. Last week I'm forcing him to sex with me on my ovulation day. (he's enjoying it too. lol. I really hope this will be a chance for me to have a baby. Its sad when your family and friends keep asking you when will you have baby but I know both of us didn't try hard to get it. Sad :( both of us didn't have any problem with marriage except for sex issues.