Nipple shields anybody?

 So my son is 6 weeks and been having trouble breastfeeding. Back and forth between bottle and breastfeeding.In the hospital the lactation consultant gave me nipple shield to use. She state I have short nipples.😕 anyways this past week I been trying breastfeed my kid straight through the weekend to practice more.  I notice that when he latch it still hurts even around my areole at times.(not sure if the shield pitch it)
My son sucks hard that I notice that the top of my nip is being pull through the nipple shield opening holes at the top. It kinda look a small blister. I finally decided to take a break from breastfeedingon day 2 from the pain. I pumped on that side I ended up having tons of blood coming out with my milk.(strawberry milk) I wonder if I need to go up in the size? If that normal with the shields? Also I find it frustrating because the shield falls off easily or will not stayin place. I have use my fingers as V shape to hold it down while my kid nurseing.  
How long am I supposed use shield?