I agree with what's been said above... but there's something else you need to consider: testosterone in any form will bring in some rapid, noticeable physical changes that your parents, teachers and friends will spot.
You cannot secretly take testosterone without them noticing.Within a few months of starting T, your voice will deepen and you'll start growing facial hair (if you're genetically predisposed to that). Whilst you probably think those sound like wonderful things, the reality is that your parents will want to know why your voice has suddenly dropped into the male range. They'll wonder why you're growing hair in unexpected places. And they'll take you to a doctor to find out what's wrong. That doctor will take blood tests and they
will find out what you've been up to.
How do you think that situation's going to go down? How much trouble do you think you'll be in when your parents discover that you've been taking illegal, potentially dangerous drugs that you bought off some random guy on the Internet without their permission and without medical supervision? Do you think you'll still be able to stay in the closet at that point? And knowing that you've effectively been lying to them about your health for months, do you think that your parents will be supportive under those circumstances?
I highly doubt it.
Your best bet is to come out to either your parents or a teacher and ask for medical help. At 14 you need hormone blockers, not testosterone: testosterone therapy is administered from age 18 in most regions. Blockers will limit the damage caused by oestrogen and they'll mean you have to undergo less surgery (or less serious surgery) later on.
But if you can't get on blockers? If your parents are completely unsupportive? Well, that's happened to many of us here, and many of us have transitioned successfully. I pass 100% as male and I started my transition at the ripe old age of 40 after having had two children.

If we can do it, you can do it... and we're happy to support you every step of the way.
Please do come back if you want more advice; we're happy to be your extended family. But please don't order testosterone online.