ive got the exaxct same problem as u, and im only in my mid 20's... i just put it down to genes, lots of food and heavy lifting,,, with me my abbs have spread since my teens, where there was once a tight line down the middle u can now fit a finger inbetween, my belly button started to herniate last time i competed too... ive never touched insulin yet, off season ive ate well over 5000 and at one point over 7000cals per day for the past 10 yrs, which i think is the main culprit.. food alergies can cause excess bloating too,,
so for me id put it down to exsess food and food alergies, heavy compound exersizes and your genes... i dont think steroids or growth have much to do with it, possibly if your mega dosing on both which u werent