thank you all for your replies!
i have an other sg, which is has the strap button at the neck base, and that works just fine.
never had issues with it, so that was part of my reasoning.
however as you have pointed out i am using a cheap strap. the one it came with.
which is very thin leather / suede, similar to this: https://www.guitarcenter.com/Franklin-Strap/3-Black-Leather-Guitar-Strap-with-Red-Stitching.gc
i think need to go shopping.
they have the same model in the shop so the best thing might be to try a few on it, starting by what you have suggested.
will post back when i find a good option, in case other people have the same issue.
cheers!