exclusively pumping

We
I've been exclusively pumping now for almost 8 months baby did latch for the first 3 months but he was really hard for him and myself since he was a preemie and it was easier to give him the bottle because he would just get frustrated on the breast and cry and cry. Now my milk is drying up I'm not producing a lot like I use to. I think I'm ready to stop. I've tried drinking a lot of water and vitamins. Not sure what else to do so I came make more milk. Any tips? Or advice?