Unity is almost unsusable

I’ve started using this program again recently and it’s extremely slow, laggy, glitchy and tends to freeze and “reload script assemblies” ALL THE TIME!!! I spend far too much time waiting for stuff to work. Sometimes I even have to go through task manager just to close it because it freezes so often. I don’t remember it being like this before.

I’m running it on a Lenovo ideapad Y570 laptop with
2.20GHz Intel Core I7-2670QM x64-based processor,
64-bit Windows 10.

I’ve updated multiple times, tried to use older versions, uninstalling and reinstalling, clearing cache, running in compatibility mode and running with -force-opengl. None of that worked.

I noticed it gets A LOT worse if I have terrain in my scene but even without it it’s pretty slow. Also “Reload Script Assemblies” takes forever. Sometimes it seems to take so long that it just reloads again as soon as it’s done. What’s going on? How can I fix this? It wasn’t nearly this bad a year ago!

Update: ok, I guess one of the updates fixed the lagginess when terrain isn’t involved (there is a little lag but its manageable and it doesn’t keep reloading). Now it’s only behaving like this if I am using terrain, which I am on two of my projects.