Natural healing is some 3 x your level per day (assuming you get looked after, and rest). Spell healing is at the rate of at least 1d8+1 per spell level cast.
And this ability gives you +1 hp per level of a spell cast? I think that banning any other form of healing would be way too harsh.
OTOH, I also think that as it stands, it's way too good.
I'd possibly suggest just giving 1 hp per spell of level 1+ cast. I honestly don't think that would be overpowering - most of the time it would be equal to or less than your natural healing rate would have been.