Breast full .. my sons 5 months.?

When I had my son, I couldnt breastfeed even though I wanted too due to complications.i tried pumping and trying to get him to latch but it wouldnt work. I fell very ill and had to bottle feed him. My breast dried up.. Then once he was 2 months old the started producing again. Doctor found it od but had no explaination. Then they dried up. At 4 months the did it again, it was very painful this time. Again no explaination. Now my sons almost 5 months in a few days and my right breast is tender and my breast are full. I got my period cycle back 4 weeks after my son was born. Could this be hhormonal? I find when they get engorged they leak colstrum sometimes