Why can't i show affection?

I find it very hard to show affection to my boyfriend. Even with past boyfriends it's been hard for me to initiate affection. I always waited until they grab my hand first, or when they kiss me first, im never the one to show it first. I don't know why i'm like that, i still struggle with it. Growing up, i never seen my parents show affection for eachother so i guess i just don't know how to act that way around the opposite . I grew up in a very male environment, where anything girlie was looked down upon. Whenever my parents, expecially my dad, saw a couple holding hands or kiss he would condemn it and say that's stupid. I don't want to have the same mentality as him, but some how it stuck with me..Please help? Im 18 and i don't want to be like this forever...