Hi
I can definitely relate to having a love for junk food! I haven't had it in 2 weeks but, trust me, boy do I miss it! My husband is like your boy-friend in which he, too, always gets junk food and offers to get some for me. We have had a major sit down and talked about the benefits of how this is not an option for me now. I have taught myself how to say no. Not that he asks me anymore, but he still is able to eat it around me and I'm perfectly fine eating something healthier.
Try to plan meals ahead of time for your busy days. This will allow you the opportunity to not make bad decisions on easy accessible fast food. Pack snacks and water to have with you all day - you can do it!
Good luck and can't wait to hear about how you do