I Think My Budgie May Be Sick Please Help :((

i just got him today and i’ve been noticing a couple if things that are making me worry, his feathers are patchy and fluffed up, he’s grinding his beak every now and then and is like leaning forward on his perch, also he has a weird yellow and black thing coming out of where i think might be his cloaca, his wings shake now and again and he often kicks one of his legs out, i can’t take him to the vet yet cause it’s late but i’m really scared for him please help :((