A model of competing pair interaction in the form of a three-Yukawa (3Y) potential is considered. The results of computer simulations show that the model proposed can describe spontaneous appearance in a homogeneous fluid of a variety of mesostructured phases. Furthermore, these self-assembly effects appear to be favored by the presence of confining walls. A field theory approach is subsequently applied to a mesoscopically homogeneous 3Y fluid at a hard wall. Explicit analytical expressions for the pair correlation function and the density profile are derived. The structure factor is calculated by introducing an effective hard core radius characteristic of the system, based on which the k-lines is constructed. It is shown that the theoretical results obtained for density profiles of a 3Y fluid near a hard wall are in a good agreement with computer simulations data.