Nipple shields?

Samantha
If this is confusing, I apologize. I'm currently nursing and have a few minutes to type this so its a little rushed. Any questions please ask I'll be monitoring all answers. 
I was given a nipple shield in the hospital because the lactation consultant said my son would not be able to latch (he can latch fine to one nipple but not the other) but didn't explain why or what a nipple shields purpose is.  
He is now three weeks old and I am trying to teach him to latch without the shield I'm not sure why he cannot latch to one but he can the other except that by visually looking at my breasts the one nipple he can't latch on is smaller and more flat I don't know if that will make a difference. I also noticed that he cannot latch at all to either nipple if I am engorged. 
I've done as much research as I can and see that most people stop using the nipple shields by now. is it OK to keep using it or is there a brand that I should be using since its long term or what should I be doing to help make sure my son latches and his nursing properly. 
Any information you can share about shields, latching, or breastfeeding tips in general are appreciated. I did not breastfeed my first, and none of my family or friends nurse so I'm kinda going in to this blind. 
M

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