You may be having issues with tensing up that's making things a little harder.
The first time is a bit scary, and finding the right angle can be a little difficult. You may also be encountering your hymen - a thin piece of skin that partially covers your vagina - this will move out of the way or break. It might be an idea to try a super clean finger to work out your anatomy and to get an understanding of where you're aiming for. It should be aimed towards your butt - make sure that you have your period when you're trying too or it's going to be super unpleasant! Have you tried the tiny tampons made for young teens?
I know it's the unknown, but try not to think about your virginity at this point. It's only going to make you more stressed. When it comes around to your virginity, you'll hopefully be in a situation where your body is all "yay sex!" and will adjust and prepare for what's happening.