Hello everyone! My son started refusing one breast, taking the second one…

Hello everyone! My son started refusing one breast, taking the second one without problems. We didn't have such a problem before, it's been about a week. He takes it only when he's sleepy, very hungry or I give him the other side first and then immediately switch. Has anyone encountered such a situation? Also, on the left breast from which he refuses milk is always more and strong pressure, but we didn't have such a problem before.