Circles Print Like Eggs!!!!! HELP!

Check, check, and check. I've done everything I can possibly think of.

Now that I don't know how to fix. I don't even know what that is. lol

Look where the X and Y drive rods are housed in the case. Should be some sort of bearing or sleeve with a housing of sorts. Make sure those are not cracked and there is no play in them. This is normally caused by a degree of give or play in the axis making the long part of the egg shape.

This printer moves the Y axis by moving the bed. Make sure there is no slop or give in the belt and make sure the pulley is secure on the motor shaft. Sam for the X which is moved on the gantry the print head rides on. Make sure there is no slop in the belt and the gear is secure. Also make sure the guide rods are square on both axis. Literally measure the space between them at both ends and the middle. Of it is not exact on all three spots then your rods are bent or the mount is wrong. A very small deviation will cause a big difference at the print head.

is there a particular voltage i should be going for?

This is not a VREF issue.  There is clearly something mechanically incorrect.  Ovals are typically caused when X isn’t operating perfectly perpendicular to Y.  In your case because the ovals are inconsistent, you have slop in the system.

Above bolded words are words confuses me. Since I'm newbie in both 3D printer and English, I have no idea what they refers to or what they means. Maybe some picture will help.

I just go read some reviews about anycubic i3 mega. Every review said it is great printer, however, the sample print they post are terrible quality. How did they conclude this is a great printer?

This printer is a basic metal frame I3 clone so I expect with proper tuning  it is capable of good prints. The trick is finding and correcting minor deficiencies.

IMHO there are a few printers out there that are cheap junk .And there are certainly well built ones, but usually expensive printers . The old adage you get what you pay for.  And in the middle ground is real life printers that take time, patience, and sometimes a few quality parts to cross that  line . We often seek the holy grail of a sub $ 300 great printer.  You save money but they take time to tweak.
In realty it usually takes a bit of effort to get the printer we have to do what it s supposed to and what we want it to do.

One one has masted his or her printer there are only a couple reasons to purchase a second third etc printer. 

1) one needs or wants a larger printer.  While one can splice parts this is of ten an unwanted task and since no one has invented a printer stretcher a larger printer can be a handy thing to have.
2)  success.  Printing so many good parts that one needs an additional printer to keep up with demand. 
3) Experience and wanting to get a real  printer. But beware there will still be a learning curve. 
I am talking real upgrade here like a ultimaker or genuine prusa .
4) wanting to build a kit to educate yourself in how a printer is built set up and tuned.

However continuously buying printers trying to find the best one is IMHO a futile effort and you end up wasting money.

I hope this helps

You don't always get what you paid for. I was amazed by the apple like design of Cube3D and read about it and it's high end model CubeX Duo, the review on amazon for CubeX Duo is flooded by angry user. It is $3,000 printer but get 77% one star review. And many comments start with give one star because 0 star is not an option.

Thanks for the clarification!