Breastfeeding and breast size problems.

Patient: Hi, I am breastfeeding to my 13 month old son and my right breast is too much smaller than the left breast.?It is looks to much difference between both and I am so worried about that. I need some help and I want to know what is the problem with my right one I am feeding with both and both breasts making milk But I don’t know why my right breast is very much smaller than left. Please help me.