People are a lot more likely to support and accept your decisions and your choices when they don't have to do anything or change in any way themselves. So if you decide to go vegetarian, and you're not already shopping for yourself, I'd suggest buying your own groceries. That way you can pick out what you want and your boyfriend or your family won't need to feel like they're forced to change just because you have decided to eat differently. If you're not the one who does the cooking, try to change that. Cook your own meals that way no one else will have to change the way they cook to accommodate your new healthy eating. Basically just take on the responsibility of handling your dietary changes yourself, and if you do that, then I really don't see what anyone else would have a problem with. Unless you're expecting them to go veg too, or only eating veg when they're around you, then they really don't need to make any changes, so it's not as if there's anything for them to be bothered by, you know?
If they don't support you, don't be afraid to ask them why. See if maybe there's something that's bothering them about the changes you've been making and if it's something you weren't aware of, but something you'd be willing to adjust, then awesome! If it's something completely ridiculous and not an acceptable reason in your opinion, then just say ok, thank them for sharing their feelings with you on the matter, and let that be that. You can't please everyone and some people may choose not to support you just because you eating cruelty-free around them, may force them to feel somewhat guilty about what they are eating. But really, that's not your problem. That's their problem. So just do what you do, try to be as independent as you can, and enjoy the yummy veggie food in the process! lol