Advice about the withdrawal method?

My boyfriend and I have sex together about once or twice a week, as we are both young adults who live on opposite sides of town, trying to save money to eventually move closer to each other. He and I are both very health conscious, and we don't believe in any kind of chemical or implantation birth control. We also may decide that we want children in the future, so getting "fixed" also isn't an option. We currently use the withdrawal method, and we have for the past two months (we used to use condoms, but they were uncomfortable on him and he had a lot of difficulty climaxing) and it's been a successful way to avoid pregnancy so far, but I just get worried that our luck will run out soon. I am only the second sexual parter he's had, so he's a bit inexperienced with the pulling out part, and I was just wondering if anyone had any really useful tips for us on how to keep this technique successful? Thank you very much in advance, much love xxxxxxx