TEGRETOL - my Carbamazepine level got higher out of a sudden, WHY is that ?

I am talking Tegretol for epilepsy and have not missed a dose however from 2 years I take Tegretol at different times. Could this be the reason why from 7 it got to 9 in 3 years time.

From to years I take my meds at different times twice a day. I take it usually at 7.30 am and in the evening at 9PM but also at 10 PM and sometimes at 10.30PM. Like I said at diferent times.

Could this have caused my increased level of Carbamazepine ??? I feel quite sleepy now and almost always tired.