Hes cheated on me,i can stop crying help?

I was seeing somebody last year who i had known for years hes 27 and i am 24 ,and last year i found out hed been seeing me and another girl telling his ex he loved her and then me,now ive found out after i took him back in june that hes seeing somebody else aswell as me again,theres photos of this girl and hes sister out drinking,i feel crushed ,i cant stop crying,hes been textn like normal today i love him and im mad about him but hes been sleeping with us both,what do i do now,should i forget i ever found out,ive never been this hurt before in my life ,i believed all the il never hurt you agains,im sittin here thinkin of when i used to tickel hes back or him play with my hair,daft things i know,i dont know why hes did it,i suffer from depression which has been under control because i had him but now if i dont deserve to have him,whats the point,i only want him,nobody else i could open up and be myself with,i trusted him and i dont normaly let people in,what now i feel like ive been kicked hard .