Feeding "frenzy"

Apologizing in advance for the long post - I have a 12 week old baby boy.  We are breastfeeding, which I am very grateful for and am loving the bonding experience with my son.  However, very early on, my pediatrician suggested using a nipple shield due to my sons aversion and difficulty nursing.  It worked like a charm.  Now my son will not nurse without the nipple shield.  I've been trying to wean him off of it for some time now - by trying to remove it mid feed or trying to get him to latch after I've pumped a bit - very few times has he remotely tried to suck without the shield but usually just gets frustrated and fussy.  In addition to this, he's more or less been refusing bottles lately.  I am staying home with him so I'm able to nurse him on command, but it does make it very difficult to leave him with anyone or go out places with him because he refuses a pacifier, too (which I'm not upset about).  He has reluctantly taken bottles in the past but lately is frustrated and fussy and can't cooperate long enough to actually eat.  We've tried different bottles and nipples.  We've tried holding him different ways and have tried to bottle feed him at times that he would normally be hungry but isn't showing signs of hunger or fussiness. When we started trying bottles, around 4 weeks, we would give one a day to get him acclimated and it seemed to help at the time but he also wasn't having as much aversion to bottles as he seems to have now.   So, I am desperately searching for *positive*, please, tips, tricks, suggestions or advice from anyone who's had past or maybe even present experience with one of, if not both of these hurdles.  Thank you in advance!