How can i get my leopard gecko to eat mealworms and why is his poo runny sometimes?

ok he is around 1-2 months old just got him 3 weeks ago almost 4 and he was climing on stuff and enjoys his tank i believe he usually sleeps all day and eats and plays at night. his temps are 85 hot and 78 cool he is on paper towel.... he has had a few runny poos over the course of 4 weeks i would say 4-12 poo s have looked runny but i dont know how to tell if its runny its brown with a white spot and its like a puddle. all the parasite leopard geckos are very sickly and dont do anything mine eats drinks alot he had 3 wax worms in a week along with some crickets and im trying meal worms which brings me to my next question he hasnt touched the bowl of worms and doesnt seem curious when i slit one in half and pput it by his face.. how can i make him intrested. Another problem is his tail its skinny im not sure if this is because he is young or lack of nutrition, if so how can i get nutrition in his body?? his tail has always been skinny but im waiting to see what will happen when his wax worms are digested because this past week or so he has been eating great! i just cant bulk up the tail?? but as far as having a parasite i couldnt see it in him he when i look at him is wide awake and alert but its funny because sometimes when i look i know he doesnt want to come out because he closes his eyes pretending to sleep haha. i woke up last night seeing him in his water bowl and he ate a wax worm and 1 cricket and the days before thw wax worms my crickets wernt fed gutload can that be the problem??? he seems to be getting bigger just not his tail