CoD MW2 tips? + classes help + general help? please!?

i’m having trouble, i keep getting killed and my kill death ratio is about 0.8, but i either exceed that and have a kdr of about 1, or much less, like i totally get smashed. The situations im in, i shoot them, or they shoot me, and usually we’re both shooting at the same time or they just kill me before i can shoot my weapon at them. most of the time i can rack up 10 kills, but then for every time i kill, i am usually killed so my kdr for these games remains as 1.

my classes go as follows:

1.
ACR + heartbeat sensor (most of the time it is good, when i use it in highrise)
M1014 + red dot
semtex + stun
scavenger pro
stopping power pro
commando pro

2. (Ghost + Anti air class)
Scar-H + Silencer
Stinger
Semtex + stun
scavenger pro
cold blooded
ninja pro

3. Sniper (yesterday i had a 28 kills, 2 assists, 1 death using this class, but after i sucked on other maps… i was on afghan)
Intervention + FMJ
TMP + Red dot
claymore + stun
sleight of hand pro
stopping power pro
steady aim pro

4.
Tar-21 + Red Dot
M1014 + Red Dot
Semtex + flash
Scavenger pro
stopping power pro
commando pro

5: Other (no idea what to put in here, so i tried to have some fun with this one.)
FAL (no attachments unlocked)
M1014 + Red dot
semtex + flash
Marathon pro
Lightweight
Ninja pro

ANY advice? please help…
PSN : Visage_7