Borderless windowed mode is capped at 60 fps

Whenever I use fullscreen mode my fps is at 600 fps if i don’t cap it, and I want to switch to windowed borderless so that using my desktop while also playing overwatch would be easier but It is capped at 60 fps for some reason, and sometimes it runs at the normal fps initially but then rapidly slows back down to 60 fps and stays there, I’m not really sure why this happens and can’t find a solution. has anyone else had this issue and has anyone found a solution for it? It would really help me out.

Xav