I'm so worried!

So I have two children from a previous relationship. My youngest is nearly 8 now and my husband and I are trying for his first. I'm 30 now and he's nearly 43. We've been trying since end of July this year when I had my mirena out. I'm so worried that we won't conceive. I've been desperate for a baby for a few years now but hubby has said if we don't conceive soon then he doesn't want to keep trying as he's getting too old to be a first time dad. What if he can't have them?! I'm now obsessed with getting pregnant and keep thinking that's half the reason I haven't conceived yet.