I did my best to play the bass in right way . But latley after a week practice I did ,my thumb muscles gets super painful . I keep my thumb behind neck sometimes a little upper for hammer one . My muscles in thumb are super painful and I can't find why its like that . I have to push my thumb to back of neck for hammer on and bending and notes on frets 1 till 3. Is it normal after one year of playing a litlte playing leave me with sire thumb muscles ?! Here example of my playing I have pain in my left thumb muscles ,is it from muscles weakness or I'm doing something wrong ?