help

i cant figure out what is wrong with me i was taking a antibiotic for a little less than 2 weeks and i was fine the whole time until like 3 days before i quit taking it...now its been about 2 or 3 weeks and i have been experiancing lower back pain and stomach cramps,and soft thin stools and i feel like i have to go to the bathroom every 30 mins but i do'nt always have to use it everytime i go to the bathroom i get a yellow slimmy mucus that comes out my anal and no stool half the time i don't know what it is i never have had this problem i usually have the problem of only pooping 2 time a week and its never been soft thin and mucusy....please help me find out whats going on? thank you   cynthia