Infertility

My husband & I have been TTC for a year and a half now with no luck. Even with 3 rounds of Clomid I still have not been able to conceive. I'm starting to feel envious towards other woman who are having children or are announcing their pregnancies. I know I should not feel this way as it is a blessing to become pregnant. Please tell me I'm not the only one who feels this way. I cry every time I get my period & just feel like it's never going to happen for us. My husband has a child from a previous relationship so I know it's not him. I love my stepson as my own but I would love the blessing to be able to expand our family. Any advice on how to handle the stress?