Please help

Okay so I started a world the other day, and I’ve spent a decent amount of time building a base with my friends. I needed some glow stone so I thought I’d just quickly go to the nether, but when I spawned in the nether I was in a tiny cave. I can’t dig out anywhere because of lava, and any other portal I place in the over world brings me to the same location. But then when I try and go back to the over world it just spawns me in this random cave no matter what I do. I lost a diamond pick and all my armour because the most recent time I went through I suffocated to death and my stuff disappeared. It’s starting to really tick me off because I really like what I’ve built in this world, and don’t want to start over.