I've been trying to meditate for a long time now. I've only been successful once. I try to get into that deep sleep, but then something will snap me back and most of the time nothing is even there.
i usually close my eyes and center on a flame that is far away, while slowly breathing, letting it become slower and longer, while getting closer and closer to the flame, as if I was getting closer and closer to my sub-conscious, but when I'm almost there, I just snap out of it. I know I'm relaxed the whole time and I know that I am not afraid. What snaps me out of it is a feeling of something moving or shifting in the room I am in, but nothing is there. I feel the energies of something, but it's not really enough for me to notice.

I dunno, I'm just confused.

That actually sounds ok to me Chloe. Have you ever tried to get in touch with any of your gaurdians or specifically see the energies working around you.
As you have already considered it you could try meditating specifically to see the energy flows in the room. Energy moves in a very different way than the physical world lets you see and a quiet looking place can have the equivalent of a tornado running through it.
You might be picking up on something like that.
OR
If it is a gaurdian that is trying to contact you by making it's presence felt. Try relaxing yourself and focussing on the flame but this time ask your guardian/s to stand behind the flame so that the light from it illuminates their face or faces.
If you see some one there, be they animal like or humanoid, speak to them and ask them to come closer so that you can communicate properly.
Before any of this though please make sure you are properly protected. Perhaps using this idea would help with that. self protection

there is also the possibility that you are stepping out of your body and the slight floaty feeling is making you feel uncomfortable ands you snap back into your body. For this you might try medittating to finish standing in front of the candle. That way you are aiming to ends up in your inner space next to your focus candle.
You can still do the other two exercises from this point but you will be able to touch your gardians from there rather than just look at them and speak to them.
I hope this helps and if you have any more questions please feel free to ask.

Zygo

The thing is is that I don't even know if I have a guardian. I've never seen or talked to a guardian. I've talked to a spirit that might have been a past life, but that's it. How do you know if the thing or person you see is your guardian?

Well the answer to that is to ask.
If you have your self properly protected ask your guardian/s to show themselves in the candle light then all you need to do is ask again.
You can also ask if there is anyone there who isn't one of your guardians and that way you know exactly who's who.

Zygo

Find a private place, somewhere peaceful and quiet where you won't be disturbed and light a candle.
Sit in front of it and gaze into the candle flame. Try to look beyond the candle flame and breath deeply and regularly.
What ever you do do not try to clear your mind, that is not possible unless you have been meditating for centuries and you'll be there forever. Try instead to find a still, quiet place inside yourself. Concentrate on your breathing and when you feel calm and quiet close your eyes and ask your Guardian to come forward and show themselves to you.
They should want to make contact with you now that you have shown yourself to be ready to meet them.