Would it look bad if I used a small stud EARRING for my monroe?

If you know all the risks, why don't you tell me them and after that tell me why it's completely idiotic to pierce with an earring. You obviously don't know anything about piercings- so grow up and go to a professional.

I may not look stupid, but it will tear up the inside of your mouth. I strongly suggest you don't. I know you think you're materials are sterile, but unless they've been autoclaved, they are not. Burning, alcohol, boiling, all of these things will kill some of the bacteria, but not all of them, especially some of the more dangerous ones. If you buy your materials presterilized, needles and everything, good for you. If you don't, you should. They're easily available online if you're over 18. But you still have to be careful not to cross contaminate; doing your piercing, you should easily go through 5 pairs of gloves or more. If you aren't, you're probably cross contaminating. Also make sure you research placement for the piercing you want. Make sure you reasonably know that you're not going to puncture a major blood vessel or nerve. I strongly suggest you have your piercing done professionally, but if you can't or won't, at least use the proper materials. In addition to the earring tearing up your mouth, the jewelry will be far too thin, you won't be able to get proper jewelry in later. The metal is probably inappropriate too. If you must do it yourself, please, at least use the proper materials. If you can get proper jewelry in 2 days, just wait until you can get the jewelry man. Two days is not that long to wait, and that way, you won't be taking risks you don't have to. Good luck, and be careful.

Chances of it staying in are extremely slim, you need a labret. An earring would not be long enough to accommodate the swelling and stay all the way through so you can do it and end up with the inside healing up. Also it will cause gum damage.

I think that'll look fine until you get the right type of earring, just make sure it's the right size post though? I did my own belly & tragus. I have various other professionally done piercings. Good luck :)