Weird feeling..

My husband and I have been trying to concieve for years, still nothing. I have ALWAYS wanted 4 children, and while I'm still in my early 20's. Lately though, I feel (only at random times) that I don't want children? But I do want them! anyone else ever feel this way? If so is it just a fear or something? I'm so confused. Maybe it's because I'm only 22. It's hard..