If she hadn't had a period since March and she hasn't been 'with you' in the biblical sense since March, and she is saying she's pregnant to your child from when you were together, her HCG result would NOT be inconclusive. She'd be in the last weeks of her 1st tri by now, so how could it be?? That's just bordering on ridiculous.
I know you're young, so will spell it out for you. You've been played. You now know you've been played. Cut her out of your life. If you don't then whatever comes next, honestly, you're partly to blame.