YOU SAID:
I lost my trousers going to school on the bus
INTO JAPANESE
バスで学校に行くズボンをなくしてしまいました
BACK INTO ENGLISH
I lost my pants to go to school by bus
INTO JAPANESE
バスで学校に行くためにズボンをなくした
BACK INTO ENGLISH
I lost my pants to go to school by bus
Come on, you can do better than that.