Breastfeeding

So my son just turned 3 months a few days ago. I got him to breastfeed the first day. But then he had to have his stomach flushed because he had a lot of fluid from delivery and wasn't latching on he wasn't harding taking a bottle and started losing weight. And in the beginning I was so exhausted and overwhelmed I cried almost everyday but now that I've gotten to sleep and am not hurting like I was I wanted to try and breastfeed again. I think my milk is pretty much dried up but I can get him to latch on he just won't stay on because he isn't getting anything from it. Has anyone been able to start back after a few months? Please I need advice