it's really hard to admit if you don't have enough milk but that is a possibility. I didn't have enough for my first son and struggled to give whatever I could until he was almost 5 months. I was able to pump out maybe one or two bottles a day, the rest was formula (at about 2 months he stopped latching on). One day it hit me that I was just done with the pumping, he wasn't latching anyway, so the pumping was adding more stress to my life and i let it go. But I was ready emotionally for it to end.
With my 2nd son, who is 8-1/2 month now, he stopped latching onto one side and I'm leaving it alone. I knew for a while it didn't produce as much milk as the other side. When I pump, maybe once every 2-3 days, one ounce comes out so I add it to the milk from the good side. I give my baby one formula bottle a day and have since the beginning so he always knew another flavor. It will click one day that you have to let go, that you can't force your baby to drink from a breast that isn't giving him what he needs. If he doesn't latch on, whatever the reason, it can't be forced and he needs to eat!! So give him what he needs.
Good luck, it's tough but in the end giving the baby what he needs is the goal.