3 years serious but 5 total. You know, my bulk/cut cycle varies. Mostly because sometimes I just eat at maintenance and recomp because I cant' be bothered to consume a lot of food or cut.
1. Genetics?
2. Reduce body fat more?
3. Do more exercises (Weighted ab exercises?)
4. If you're really desperate make sure you're getting all your abdominals upper, lower, obliques, etc...
5....
Listen man, When I started I jumped right into a 5 day split. It was fine just dont go crazy on volume. A lot of people here will advocate strength work first. I'll agree with that too.