JanexHopper

I'm fairly new to mesh making and I just recently figured out how to rig a mesh, so I made a shirt, it's properly deformed in blender, all bones are linked to the right area in weight paint mode (1(2).png) but when I try to upload it, it is rotated to Y-axis (22.png) and when I include skin weight, it is completely ruined (3.png) And it is actually how it looks like if I upload it and wear it. I've searched everywhere but can't really find a solution to this, I'd really appreciate it if you guys can give me some useful tips!