Losing my mind a little

My little one is 1.5 months and she is latching just fine. However, lately she has been sleeping for 5 hours and then feeding 4-5 times for 2 hours straight. I eventually run out of milk and have to supplement with formula. Anyone else have this problem? I have tried to waking her to feed her and she takes very little and doesn't want anymore. Unless she cries, she won't do a full feeding. I feel like this isn't normal but I am just trying to figure out if it is a supply issue or what in the world is happening... Thoughts anyone?