The effects of polymer concentration and chain length on aggregation in associative polymer solutions, are studied using self-consistent field lattice model. Only two inhomogenous morphologies, i.e. microfluctuation homogenous (MFH) and micelle morphologies, are observed in the systems with different chain lengths. The temperatures at which the above two inhomogenous morphologies first appear, which are denoted by T_MFH and T_m, respectively, are dependent on polymer concentration and chain length. The variation of the logarithm of critical MFH concentration with the logarithm of chain length fulfils a linear-fitting relationship with a slope equaling -1. Furthermore, the variation of the average volume fraction of stickers at the micellar core (AVFSM) with polymer concentration and chain length is focused in the system at T_m. It is founded by calculations that the above behavior of AVFSM, is explained in terms of intrachain and interchain associations.