Hun your story sounds like mine...are you making enough milk now? I have twins and had the same issues as you. Finally at 10 weeks I started exclusively Bf without shields and my life became easier! I put them on the breast first with the shield, then would take it off. Experiment though..maybe try to latch him first without, then add it on later when he gets tired, just try without for a period of time at EVERY feed. My one son was lazy and just wanted to use the shield, the other one eventually hated the shield and would knock it off and latch on!!! I remember the glorious day, LOL! Don't be surprised if you "regress"...my lazy son would latch without the sheild, then all of the sudden couldn't latch without it!!! It was disappointing, but with work you can do it.
I also had to top up my twins with ebm or formula....I pumped after every single feed, even in the night! At first I couldn't keep up with the demand, but eventually we weren't feeding any formula at all. Once I was reassured that I made enough, we went on to EBF. I'm not saying this is for everyone, but I was very determined.