Feel so lost

So last sat i caught my bf cheating to make it worse he confessed he is a Dom and that girl is his Sub......... Who knew friends for yrs together a little over a year 2 miscarriages in the last 6 months I feel lost he is begging me not to walk away he loves me he will give it up ( So confused i feel like i walk in a daze) I dunno what to believe what to do I was always so strong and then Him its soo hard to walk away from ahhhhhhh