How to move on

How can you move on from your SO/husband when you find dirty videos in his phone and hear him saying he wants to be with someone else and you are six months pregnant. I feel like it should be easy, but it's not it's really hard. We have two kids together this is our third, he begged to have this baby with me we have been married for 8 years and together for 14yrs. I guess it's really hard because I just want that partnership/relationship throughout this pregnancy and not do it alone, emotions are high enough.