cf and work???

Well i been working all most for as long as i can remember. i went from working 6 to 7 days a week down to 2 days a week. Well now im barly working 2 days. im always sick anymore. recurrent brochitus or phenomia infections. Well im afraid im going to get fired. can they do this? even tho i been with em for liek 3 yrs. can they really fire me for missing to much work? i have ssi and disabilty pending as of now. but i have a son to take care. i cant wait for this to get approved. i have bills to pay. what do i do? any suggestions would greatly be appreciated. oh and yes my work knows about my cf.

thanks for the advise burn however, i talked to my boss, he told me sunday that my job was on the line. he said hes got a business to run. can they really fire me for being sick all the time? its not my fault. i never asked for this.