Feeling like I'm sitting on my chair and not in it?

Pretty much just what the title says. I'm always sliding forwards in my chair as well, and constantly have to scoot back. I wanted to adjust the dump on my chair but I can't get the screws out (and my ATP can't come out for another few weeks at best). Does anyone know any at home fixes for this? Or is it worth it to go to a bike shop and get the screws out?

For a bit of extra info I have a TiLite Aero Z and have been using it for around 10 months. I didn't have this issue when I first got it, but my condition has degraded since then.