HELP!!

So, my husband and I (mainly me) have been trying to have another baby for a while now. Our daughter is 1 1/2, and we want our children close in age. My periods are fairly regular. Always 30-32 cycles. They generally are always the 1st (or within a day) of the month. When I got pregnant with my daughter, it was exactly a week after I ended my period. After having her, I tried taking ovulation tests to predict when I would be fertile, but none of them even worked. I also tried having sex in my predicted fertile window. That didn't work either. I tried having sex the week after my period like how I got pregnant the first time. Still nothing. Is it possible to become infertile after having one baby?? I really want another one and I'm starting to get really discouraged.