leukemia??

Hi all! My son is 8 years old and a typical little man, BUT i am having so real concerns and i was just wondering if i am over reacting. Ok here goes, Like i said he is 8 and already has terrible acid reflux, it is to the point of reguritation (throws up in mouth). i have noticed he bruises really easy, tested it one day i just poked his leg and the next day he had a huge burise that lastet for almost 3 weeks. he has severe constipation where he doubles over in pain and sometimes vomits because of it. also astma, i have looked online and all these symptoms together head me to leukemia! In your opinion should i be concerend, could this be leukemia? Have you heard of anyone having any of these symptoms, Please help!