Dog Licks Its Butt Alot My Dog Has A Problem..what Is It??

My dog has a problem..what is it?? - dog licks its butt alot

Ok my father about her year and a half and a Shorkie. The recently Alotta scratching and licking my legs and back of the status Obession, bite and sting. He was arrested several times for fleas, ticks, etc., but to no avail, have also bought, not to kill the first line drug for all. What is wrong with him? And a dog may be indicated as many baths, flush with only well with water? And strange one last question, it is normal for a dog his age who have loose skin, keep it a little strange, but my brother can wear the neck and drag up, again? It tightens and his strange, but my brothers .. So strange, hehe, what's all this .. is bad, or what?