Trying to gain weight. HELP

Jasssyyyyy

All my life i haven’t been able to pass 110lbs i eat junk food and healthy food too and it hasn’t given me any fat or helped me gain weight. My family has always been telling me I’m too skinny, that i need more meat on my bones and that I’m going to get sick from being too skinny. No don’t starve myself i eat whenever I’m hungry or feel like eating. Ive been working out and going to the gym since November and still no signs of gaining weight or muscle does anyone have any tips on how to gain muscle on legs an booty preferably. But any advice helps, here is how my body looks like i just want my arms to be fuller and legs too thanks guys !