Milk supply just keeps doing down

My girl is 20 months. My milk supply has been going down since my period return 5 months back. Now I'm barely expressing about 60 to 80 ml per day (have to combine 3 days milk for 1 feed). Is this like a sign that I should stop breastfeeding? I am reluctant to end the journey cause this probably my last. But the yield is so pathetic that I dont know if I should still try to increase my yield. Anyone has such struggle?