We've adopted him yesterday, he's 3 years old husky/malamute mix (and he also got worming pill). When I took him for a walk he had normal stool, but after that he had diarrhea twice. In the evening I gave him rice and minced beef with some carrot and he had diarrhea at like 4am. When I gave him another walk this morning, he just peed.
After that he ate some dry food and minced beef with rice again - his stool was hard but after that, he had diarrhea again.

Otherwise he's still a happy go lucky dog. I don't know what to do, I don't see any worms in his stool, but he's showing signs of having them and i'm really worried? :/

Try giving him straight rice and some boiled chicken with no seasoning or salt.. or others have used scrambled eggs with veggies with no salt. Also, greek plain yogurt or pumpkin filling out of the can can help settle a husky tummy. I used to mix yogurt into Dragon's food every once in awhile to keep his stool regular and sometimes as a treat (he loves the stuff) so I would try one or two of those options. Just don't do too much because too much food can cause diarrhea. If you're feeding him more than 2 cups a meal that could be the cause of his irregular bowel movements.