Fps lag

Hey guys,

I've noticed lately that I've been getting fps lags 24/7 it's steady around 27 and 30 is its cap. How can I get to improve this?
On retail I run 100fps+ everything on ultra even during boss fights. And in PUBG(Playerunknown's battleground) I run around 60-80 fps everything ultra and high. So we can conclude it's not my pc from this I suppose. But is my fps capped at 30 or is there a way to increase it? Because I can guarantee it's not the pc. So that's why I've come here if anyone could help me out I'd greatly appreciate it.

Thanks in advance!