D.B.
T., I am glad you decided to reach out to experienced parents.
First of all, please resist the urge to make this "not a big deal" - if you are living under stress, which is understandable, then it's a big deal. You are who you are, and I hope that your parents love you enough to accept you as your true authentic self. There are many people who are serious about the Bible who are very welcoming to gay people in every way, including gay marriage. And it's good that you admit you don't know what their views and beliefs are.
Also, some parents who don't react well to this news aren't necessarily anti-gay. Many don't wish this for their kids because they worry about discrimination, and they don't wish for their kids to have pain or to be in danger from homophobic individuals. There are also parents who have trouble thinking of their kids as having sexual feelings, so they may ask questions like "Are you sure?" or "How do you know?" That doesn't make them anti-gay, it just means they aren't too comfortable with sexuality in kids. And they may have concerns about a 14 year old being sexually active, whether that child is gay, straight, or bisexual.
Is there someone you would be comfortable talking to first? An uncle, a guidance counselor, your pediatrician (you are old enough to call that doctor on your own), a minister or church leader familiar with your parents' beliefs?
Another option is to preface your remarks with your concerns about not knowing their views on something, and your need for their support. You might also say that you have something to share and you hope they will let you finish before they react. Say that something has been on your mind and you want them to be involved/aware, but you are concerned that they will think less of you. Tell them you love them, and you want their love and hope it is unconditional. (They will probably reassure you at this point.) THEN you say that what you want to share is that you are gay. They may well be very relieved that there is nothing wrong with you (you're not sick, you haven't committed a crime, etc. - in those 60 seconds that it takes to tell parents you have something pressing to talk about, that you need them, etc., all kinds of things go through their minds! If you have not be sexually active up to this point, add that in, to reassure them.
You can also consider writing down what you want to say, and reading it to them so you say everything you want to, don't leave anything out. That's up to you. Some teens would rather just talk without the notes - but either way is fine.
If they don't react well, just reiterate that you need them, that you are the same kid they knew and love 5 minutes ago and yesterday and 2 years ago. If they bring up Biblical prohibitions, you can say (truthfully) that you respect their beliefs but you also know that many religious people and religious leaders feel the opposite, that the Bible requires us to be kind to each other.
Is there any reason you would feel unsafe in this setting? Do your parents have a habit of reacting with extreme anger or even violence? Then I would definitely have someone else with you.
Good luck and let us know how you do!