I often hear this from people, trying to find the "right time" to start. Quite simply, NOW.
12 weeks in the line you will wish you have started today and not 3 months later. Let's face the facts that there always going to be someone's birthday to celebrate, there always going to be a work lunch, date-night, Easter, Christmas, you name it. Would not be easier to be able to handle those situations? Learn how to stay on track while you are out? Learn that,this is not a failure, this a challenge to help you move forward.
Would not be easier to finally be a bit easier on yourself and realise that these occasions are not failures, these occasions are lessons for you to learn from. You don't have to be "on-track" or "off-track", just need to learn from the times when you couldn't control everything.