Trying, but scared

My boyfriend and I have been trying to get pregnant. I had a miscarriage in February at 7 weeks and it devastated both of us. I have 3 healthy kids, the youngest being 6 and before now I have never had to "try" to get pregnant. I'm starting to get worried that maybe it just isn't meant go happen for us, but I'm also trying really hard to remain patient and pray for the best. He has no biological children, and I would love to give him this gift.