Hi OP,
I understand why you're confused and a bit....alarmed maybe, but try to relax. You are certainly not alone with these feelings, as you can see! 
It's very common to be questioning your sexuality later in life.
One piece of advice I would give though is, don't do the whole "free pass" thing, unless you're in an open relationship that is. It never ends well and I think some men underestimate the intensity two women can have when they become intimate, so give the green light and then things can get messy.
I came out at 28 and met and fell in love with my now, gf. I had a 9year relationship with a man before that and a 5 year old dc at the time. It was scary, yes. It was slightly harder knowing that nobody would ever suspect I was bi or gay. I'm very feminine, which some people still can't seem to understand. My parents were homophobic, which was obviously adding to my fear of coming out, because we were\ are very close and I cared about what they thought, even though I wholeheartedly disagreed with their views.
Fast forward nearly 5 years and my parents love my DP to pieces! Things were a bit rocky at first, but things changed very quickly once they saw how lovely my dp is and how happy she makes me. They would be devastated if we were to break up now, as would my dd. Yes, I was also concerned about coming out with a dc, because of the risk of homophobic bullying, but apart from the odd silly comment, there's been nothing. Thankfully.
If someone had said to me as a child, or in my teens, or actually any time before meeting my gf 
that I would be living with and planning to marry a woman, I wouldn't have believed them for a second.
What are you specifically afraid of OP?