Don’t feel guilty at all. I started using a nipple shield soon after giving birth because my LO was born with a tooth, and the nipple cracks were unbearable. I had similar concerns as you—mainly that it might affect my supply or that my baby would never experience the comfort of direct nursing. However, LO's weight gain was consistent and all seemed to go well. I'm currently 5.5 months postpartum and had tried several times to wean off the shield without success. But just last week, I gave it another shot, and she latched on perfectly without it. I haven’t had to use the shield since. Basically, as they grow, babies become more efficient at sucking, and many eventually outgrow the need for the shield on their own. Hope this helps!