Advice please

My boyfriend of 3 years has been with girls behind my back, i found out from a photo i ended up seeing! He said im a piece of shit at the bottom of his shoe and he also said he doesnt care about how i feel.

We also have a baby together. Feel so useless. Hes lost alot of interest in me so its all going on the girl hes been with.. only time he wants to know me is for sex. Never invites me out, never asks to come over or to stay over.. im the one doing all the effort, literally one sided effort. All of his effort is going into someone else 😞