Question Why am I getting lag?

[SlicingYeti]

It's been going on for a few weeks now. I have a 250Mbps internet package which has never let me down before, even in peak times (I know you never get the advertised speeds, but every time I've tested it I get around 200, which is plenty for gaming and no other devices on in the house), but nothing I've done to try and rectify the lag has helped, I've downloaded a Ping booster program to see if it helps, it hasn't made any difference it seems.
Take my last COD match for example, connected to a London server (I'm in the UK) I had a ping of 65, jitter was 8.1, and no packet loss, quite decent numbers I thought. Yet I was still jumping around and freezing up?!
Is it the games fault? My ISP? Something on my PC???
It doesn't seem to make a difference what game I am on, or server (I've tried Germany servers with Battlefield 5 & 4), and various EU servers with Tarkov...
At my wits end here as it's ruining every online game that I play, which is pretty much the only social I get with my mates in lockdown! >.<

 

[SlicingYeti]

Oh, and to try and head off some potential replies:
I used a wired connection direct from router to PC, the only other devices on the network would be the TV (wired) and 1 mobile (wireless),
I don't have any other programs running on the PC while gaming except Discord,
I don't use a VPN,
I used to have an average ping of around 30 a month ago....
Thankyou