I feel the same. I find in these moments just focus on surviving rather than kills or objective. I'll often have full days like this.

I'm terrible at PvP, but I find I'm even worse under certain conditions. A: game in progress. If I spawn into a match that's already underway, whether I'm on the winning team or not, I just can't seem to get it together. B: my weapon perks. When I get a new gun that I absolutely love, it takes a while to get a feel for it. It can be the same gun, but different perks, and it will feel completely different. The weapon perks change how it behaves. C: I don't know why, but I do better when matched up with randoms than I do if I'm in a fire team. Its weird I know, but in a fire team with friends I do way worse than normal. Also I've found if I have a couple of killer games, suddenly the enemy fire teams get harder (maybe sbmm?) And then some days are just bad days.... Best of luck man.

Did you take a break, that tends to be one of the problems, your not fine tuned to this game anymore, as with me

You're definitely not bad, it just takes a lot of practice and patience. Not playing mad is a big factor I think, a good fireteam helps as well. Don't charge people if you have medium to long range weapons, etc. SBMM makes it a tad harder IMO