Trouble with sail trim on my boat

I've been sailing my boat for a while now, and I've been having some issues with getting the sail trim just right. I feel like I've tried everything, but I just can't seem to get it to perform the way I want it to. Maybe someone here can offer some advice? I've been noticing that when I'm sailing upwind, the sail tends to luff a bit, and I'm not sure if it's because of the way I've got the sheets set up or if it's something to do with the mast orientation. I've tried adjusting the boom vang and the outhaul, but nothing seems to be making a huge difference. I'm starting to think that it might be something to do with the sail itself, but I'm not really sure. Does anyone have any experience with this kind of thing? 🤔 I'd really appreciate any tips or suggestions you might have. I've been sailing for a while, but I'm always looking to learn and improve, and I feel like this is something that's really holding me back.