Baby Fever

I'm ready to have a child. I'd go to the Sperm bank, but then my boyfriend will probably think I cheated. My boyfriend and I love each other but He has two children already. We casually discussed starting a family together. He says he wants kids with me but people can say anything. However, I seriously want a baby. I don't care if we coparent. I don't care if I'm a single mother. I'm not big on marriage. I just want a child of my own (no adoption) and I fear my time is soon to be running out. Biology and all. && some women take like 7 years to become pregnant. I'd be extremely devestated if I didn't have children. Any suggestions of How I should bring up the topic and let him know I want us to work towards having a baby ??