TTC... Sometimes

Hi folks,
​I'm in my late twenties, my DH is in his early thirties, so we're at the point in our lives when all of our friends are making little people. I have always had a strong desire to have children and with all these pregnant woman and adorable toddlers scrambling around, I'm starting to feel left out. DH and I both really want kids and I'm pretty gung-ho about TTC. He still seems hesitant. There have been a couple of unsuccessful attempts, but they're always on his terms and not during optimal times of my cycle. When I try to bring up perhaps timing things better, he shuts down. Quite frankly, I can't deal with the roller coaster anymore. I don't want to say that we need to stop trying because if there is the slightest chance I could get pregnant, I don't want to miss out. On the other hand, if we're not going to give this full effort, I can't handle the disappointment... How can I approach this? How do I cope with the idea that we will have to stop trying until who-knows-when?