I haven't touched it, either.

And I agree with Sureboss & Blitz, I'm also rather up & down. Much more so than in CoD4. I've gotten that over 10 kill/death thing in bunch of games. Steamroller, MVP, etc. But some games, I'm struggling to finish with an even k/d ratio. I think team making has been laughable, too, but that is nothing new!
I dont mean to moan, im just asking for advice !
Oh, you know we are full of
it. good advice!
Although there could be countless reasons why someone struggle on regular team deathmatches, I'd start with this: Play slow.
I don't mean just stay in a building with a LMG, go hide in the corner. But move slow, and from a cover to cover. Let them run into your sight, not the other way around. Also, look around a lot, pay attention to the
whole screen for anybody, any movements.
I have more tips I'm gonna list, but you don't have to read them all. Also, keep in mind that Hardcore & Free-for-All are very different from normal TDMs, but your struggles might not have to do with any of that. I encounter so many unexplainables(not a real word) & coincedences, it's not even funny:
Most important might be just being ready for the match. Do you know your way around the map? If you don't, make sure to check out the layout in private match mode. And once you learn the maps, study how teams like to begin the match. You could score couple kills easily, and very quickly, if you know where the other team like to camp, or route they take at the beginning of the matches. Being able to predict much of their movement makes for easier TDMs.
Once you know your way around the map, get an idea of how the enemy might operate on it, you can start choosing the right gear to go in the match with. If you do well on Hardcore, but not on the regular TDMs, maybe you need more stopping power. Or maybe you need longer range, or quicker spray & pray(P90 baby!). Experiment, find what works for you. Personally, I recommend working towards a thermal scope upgrade on something like M4, ACR, SCAR. Not great for close range, but excellent from mid to long distance.
I'll make this the last one, use a cannon fodder.

Let some sucker lead, you still move from cover to cover, when the enemy start shooting at the cannon fodder, you shoot back!

You don't have to blatantly steal kills, but try operating behind your teammates(halfway decent one's). Operating in numbers is not a bad idea sometimes in TDMs.
I haven't really done any online in MW2 yet - too busy getting married
Congratulations, Famine! 👍 Go easy on the video games, (soon-to-be)married man.
Don't worry, i've slowly been getting worse the more i play.
Starting to get an urge more and more to go back to CoD4.
What level are you at? Because I think improved toys & perks they give you at higher ranks, they can certainly help. Also, I think(this goes for barryl as well) kill streak set up can always be tweaked. If you are not getting long enough streak, you could go for a something like 3-4-5, ending with a Predator missile.
Don't give up yet, and there will be bunch more noobs(like Famine!) who will join in late, come December, and we will feast on them!

Just keep working at it. 👍