My roasts ALWAYS overcooks!!! Please help!!!

Hi everyone. First time posting on this sub.

I had made several Mississippi pot roasts over the past few months. I’ve used two slow cookers - one used 6 qt. Crockpot, and one 4 quart new Crockpot. Just in case the bigger crockpot was over cooking my roast. The recipe I used calls for a 3lb. Roast cooked on low for 8 hours. I can never find a 3 lb. roast. I usually find a 2.3-2.5 pound roast. Today I checked my 2.4 pound roast cooking on low in the 4 qt. Crockpot for 4 hours. And it was already over cooked. About 190 degrees with a food thermometer. There was a little pink in some spots, but it was NOT fork tender at the slightest. It’s rubbery.

PLEASE HELP. I fail miserably at cooking roasts in these crock pots each time. It’s not the crockpot because both crockpots I’ve used overcook the roasts. I use crockpot liners but I can’t find anything on the internet about liners contributing to over cooked food.

What should I do? Ditch the liners? Cook it on high? The recipe doesn’t call for any liquid in the pot. Just ranch dry mix, onion soup mix, butter and peppers. Should there be water or broth added? IDK. I’m about to give up on slow cooking roasts and just go straight to the oven or something. PLEASE HELP. I’m pregnant and emotional so it doesn’t help my frustration.