Low milk on one side

Kim
So I've noticed in the last week my daughter has pretty much hated eating on my left side sometimes won't do it unless she's in a football hold which isn't very easy cuz she's 3 1/2 months old, and I can clearly see the difference in size between my left and right... At night I always feel like I have no milk at all she woke up at 2am last night and I tried to nurse her back to sleep but it was jus hurting my nipples cuz nothing was coming out it had been only 2 hrs since she had nursed last, so I gave her some formula which she hasn't gotten very often but she wouldn't go back to sleep... Now she has been sleeping for 5 hrs and I jus pumped both sides my right I got 4 1/2 oz and left I only got about 1 oz... Anyone have any ideas what I can do to increase the left and increase my supply in general cuz the afternoons to night time I always feel like she's barely getting anything even from the right... Morning is the only time I feel full and can feel my let down now, I use to feel it all day every time but not anymore