Once or twice per year, I feel like throwing my whole wardrobe out, and just go for jeans, t-shirt, badly fitting hoodies and battered old sneakers. Because frankly, it doesn't feel like anyone gives a shit that you make an effort to look good. In fact, it quite often feels like it's a source of resentment. So when confidence wanes, it's natural to not want to stand out. Standing out requires confidence and a belief in what you're doing.
Because I have young children, who periodically are very demanding, I sometimes can't bring myself to spend even five minutes ironing a shirt, and I refuse to wear a wrinkled, unironed shirt. Then it's hard to keep it up. Especially since most people won't even take notice if your shirt is ironed or not.
Perhaps there's something in your life at the moment that takes more energy than usual? That can take a toll on confidence, or make it hard to keep an interest up. Your confidence will return, I'm sure.