Are you rapidly gaining weight? Or are you just buying clothes to small hoping you will lose weight? Either way discuss this with your mom and sister, today.
I really want to tell my mom or my sister that I'm struggling with this. I already bought size 2 and 4 clothing and am embarrassed that I now need 6. I want help but don't know how to ask for it?
Nothing to be embarrassed about. Discuss this to your mother. She is your mother, she'll listen to you and will do her best for you.
This is your requirement, you shouldn't hurt yourself psychologically like this. Go forward and share the topic.
I'm not even sure how this gain is impacting you but since you sound a bit worried i see it right to tell you, that's right fitness and equal weight is healthier and considered suit but remember, gaining weight is not an embarrassing matter. Sizes are the least important factor whether in relationships or achievements. Most importantly, it never determine who you are as a person from the inside. At the end of day, be yourself,embrace yourself and never be ashamed of such.
We have no idea how old you are or what your health and physical condition is. If you're concerned, tell your Mom. She'll want to help you feel better about this or get help if you need it. Don't obsess over sizes. It's more about how you look and feel and if you're healthy.