It's one of the hardest parts of our transitions: coming out.
You can start giving small hints of how femine you are, showing that you care about your appearance and want it to look more feminine...you can start behaving more feminine...but sometimes our parents are just too blind to realize anything.
My parents never even had a clue I was trans. I gave them a lot of clues and on the last year I was giving a lot more on porpose, but they didn't realize until the day I decided to call my mother and tell her everything.
I never had a girlfriend (and I am with almost 27), never behaved on very masculine patterns...but they never thought anything was wrong with me. I wasn't even considered gay...they just thought I was kind of delayed and that some day my instincts woiuld wake up and from that day on I would start acting as a "normal" boy.
But here's mu advice: There is no way to run out. One day you'll have to call your mom and say it all. Get ready, choose the right words and tell her everything. You'll feel much better after coming out

, even if the results aren't the ones you want to expect.
I started remembering my mother of the feminine traits I have and telling her that I secretley crossdressed since I was 8. I told her how I was envious of women and how I would like to be accepted and seem as a woman. It was very hard for her to understand and accept me. Sometimes she was already treating me by feminine pronouns and giving me some of her old feminine clothes...sometimes she was in denial...but I am happy she had the chance to know my real me before she have gone a few days ago