Falling in love is not allow ?

Hi, I been with my boyfriend nearly 6 months. We were best friends for ages before that and then one drunken night i admit my feelings and he admit his and we had a great night togther. We both agree that night (althought very drunk and horny) that we wouldnt have sex unless this was going anywhere. and what did i know i end up falling in love with one of my best friends. I never ever like to admit love as i never understood how you can fall in love so quickly but i do believe i have. When i told him i was so scared and the best thing ever was he said it back to me. He always says love you when i say goodbye to me on the phone. My only problem is my family dont really like me saying it when i went on hoilday with them my sister ask "you dont always go love you, miss you do you?" i said "why are you asking" and she said "because its silly when people do" and i use to be like it a little only because she was. But now i know how it feels to be in love and miss someone all the time. i just dont know how to explan to them my feelings and for them to not look at me differently.
I also want to tell them that i am sleeping with my boyfriend. I really shock they dont know as i stay around his a lot. My mum has ask if i was having sex and i said no (this was before i was having sex) and my sister has ask if i sleep in the same bed and i said yes. But they still dont think i am having sex.

Any advice at all? Thanks in advance xxx