Is there something wrong with my back ? ?

Well im only 21 right now. Ive had occasional back issues since i was 16 or 17. Even when I was younger after i run my lower back is sometimes sore. I have flat feet which im sure does not help matters. But when I was 16 was the first time i actually was in pain. I was swinging a bat and all of a sudden my lower back hurt badly. But it seemed like if I layed down it would hurt more and in the mornings it hurt but once i get up and walk around a bit it starts to feel better. After a day or two it feels 100% again. This same type of injury happened probably 10 times since then. Recently it seems to always involve being hunched over for a long period while doing strenuous work. It does not seem to be an injury that is muscle related. Maging and rubbing the area does nothing to make it feel better. Also Ive been using a machine at the gym for my lower back and I can do a large amount of weight with no issues at all. I also do alot of abdominal work. One issue ive found though is that when on an inclined bench doing abs if i lean back putting alot of stress of my lower abs and back i hear a small pop each time. It does not hurt it just worries me alittle bit. Im not sure if this is a problem ociated with my flat feet, a disk, a nerve or something else.