Hmm.... I also mostly play LMGs, but the thing is, they're generally not very good in super close quarters because of their handling. So in those fights, it's normal to get shredded a lot.
Now, they did just add the canted foregrip to LMGs which gives them really good hipfire. If you're comfortable with hipfire, I'd put one of those on one of the fast LMGs, add a green laser and just hose people without aiming. Mk123 is really good this way in my experience.
If you're not comfortable with hipfire, I'd suggest you practice it and get used to it, you can pull off clutch kills with it.
But some people just never really take to it.
If that's you, I'd take something very middle of the road for handling/damage. I'd suggest assault rifles, maybe the EF88 or B36. They're both all arounders as far as damage/range/recoil etc. If you're an lmg main I think assault rifles are gonna be a natural shift, since they won't have the severe damage drop off that carbines and smgs have, but still handle better than LMGs.
Just use them for a while, don't switch around, and try and evaluate what may or may not be working out. If you're losing a lot with them in close quarters, chances are you may want a gun with a more aggressive rate of fire/higher dps. If you're losing out over longer distances, you might wanna try the AK4D, L85 or even SOR. AK4D can still win at all ranges if you're handy with recoil/bursting.
How you feel about DMRs?