Initiation fear

Me and my boyfriend have been together for 2 years. He always says he would like me to initiate it but I've tried a couple times and each time he turned me down because bad timing I guess. We haven't had sex for 3 weeks and only maybe 4 times since we've had my 6 month old twins. I would love to be able to initiate sex and I've thought about but always get scared. Even buzzed. Each night this week I've thought about trying but then he goes to bed before I even can. Any tips on getting over it?