Hamstring Pop

so long story short, I felt a pop in my right hammy during a sprint workout a couple of weeks ago. I iced it on and off and stretched it for a week then in week two i started walking on the treadmill and resumed upper body weight work. Then two weeks post pop i felt the same pop again chasing my dog down the street and am back at square one.

if any of this info helps, i tend to go through cycles where my lower back nags, this usually goes away with better dieting and core work. I also am notoriously not flexible, and can barely reach halfway down my legs in the classic hamstring stretch. I have no real injury history though. I had recently stepped up deadlifts of the straight leg variety and cut back on the squats.

Also an FYI, I was cursed with the Justin Beiber body type, so im a scrawny dude with a shorter torso and longer legs (if that helps for anything)…

Any advice on how to rehab the leg and work sprints/hills and lower body days back into my workout regime? losing the definition in the legs, packing on fat in the mid section, and being in poorer condition overall is killing my vibe.

thanks in advance guys