Need HUGS. perfect life and lots of money but CANNOT HAVE MY MUCH WANTED BABY?

Can you offer me some words of comfort. I'm a 27yr old female. I've been trying non stop this past 5 months to get pregnant, and im really disheartened. I have everything i want in life but i seem to have difficutly conceiving and i'm scared i'll be too old as I'm only 3yrs away from the BIG 30. I was hoping to have my childrearing done by then. I'm very fortunate, my husbands very wealthy and we have everything we want in life. I've got a great housekeeper and childminder. It means i'm fresh and able for my children every day and my time with them is special not fraught over the banal domesticities of life. My husband agrees. My children are 6yrs ( a little boy), 4yrs (a little girl), and twins 18 months ( 2 little boys). I'm just really desperate to have another little girl and feel so sad that i'm not conceiving. The rest of the pregnancies happened within weeks of trying. is there something wrong with me? I 'm beginning to feel UNFEMININE as someone has suggested getting help. If i have to do this i will feel like a failure (that i am not working as a woman should be) and would be horrified to have to resort to ivf or the like. Please help. My clock is ticking, BIG 30 approaching and I just want one or two more babies to complete our perfect fammily and life.