Re: nipple shield
If you have sore nipples and ESPECIALLY if you have the tube of lipstick look going on, she almost assuredly has a tongue tie.
Unfortunately, most lactation consultants at hospitals are told per many hospital policies to downplay tongue ties. Find a private lactation consultant, one preferably who is a le Leches league leader.
With doctors, unless you have a rare pediatrician, again, many do not believe in the significance of tongue ties and many believe in the "wait and see approach". In other words, they would rather wait to see if the child develops speech problems later in life to correct.
Tongue ties, especially posterior tongue ties, are woefully under diagnosed.
Start with a local LLLL. I would bet money your LO has a tie. You get the lipstick nipple because instead of her tongue cupping your breast the way a normal child would do it and creating the wave motion, the only way she can do it with a tie is to press your nipple on to the upper palate - which causes soreness/pain and that classic lipstick tube look.
As far as the sleeping, it's common around growth spurts for them to be extra clingy. They are gaining new capabilities and don't quite know how to cope yet, so they need the extra comfort.
There is no such thing as spoiling an infant under 6 months =).
As for all this tongue tie stuff, I am just finishing all this up with my little one and it's exactly as you described - up to lactation consultants not finding it and his pediatrician saying "it's not a big deal".
We went to a dentist who lasered the tie - next to no bleeding and much faster dealing time.
Good luck!