With DD1, I had tiny amounts of milk present for more than a year after complete weaning (I weaned her really young). They only went away when I got pregnant with the twins. They've been weaned since June (please no crap about my early weaning-- I have serious health problems) and I still have tiny drops of yellowish milk.
If you keep squeezing them "just to see what's there," (I always did too!) you'll be giving just enough stimulation to encourage a tiny amount of continued production. The only way to make it stop is to completely stop trying to express anything.
But it sounds like you have quite a lot. If you haven't expressed any at all, it might just have been building up in there. It can take a long time for those last bits of milk to be reabsorbed, and for your body to stop producing, especially if you nursed a long time.
I think it's fine, and I wouldn't worry about it.