Thanks, that makes a huge difference. Here are the options as I see it if you want to multiclass
1) 2 levels Bear Barbarian - You can rage 2 times a day to get advantage on grapple checks and get more damage. Plus you get crazy resistances against damage. That will help mitigate the lower AC
2) 2+ levels rogue. More damage with sneak attack, bonus disengages to move around more to avoid the hits. Plus expertise with Athletics for grappling goodness
3) 2 Levels fighter for Action Surge, Second Wind, Heavy Armor proficiency, and a Second fighting style. You can take the defensive fighting style and up your AC massively
4) Continue on a Gloomstalker
It sounds to me that a Bear Barbarian would be awesome for your character.