No idea how I feel or what to do...

I always felt suspicious about this woman around my husband. Call it intuition I'm not sure but I didn't like her from the moment I met her. I confronted her once and asked if she was messing around with him and she swore they were friends and kinda abused me for insinuating anything. I felt really dumb and even slightly crazy. My husband denied anything was going on too. Life moved on. We got married, had 3 kids....

3 weeks ago we are at this party and we download an app that synced to his friends devices or some shit. He hadn't spoke to this woman in 2 years, she still had his number. She sends him messages. Me, slightly intoxicated decided to message her and have a bit of a crazy moment telling her to stop messaging my husband. I just did not like her and never felt good around her. Anyway she bomboards me with dirty text messages from 2016 between her and my husband 1 month before he proposed to me. He was initiating a lot of it, she was asking where I was if I was asleep, she knew all about me never once pulled him up on it or told me (was around the same time I confronted them both and they swore nothing was going on) ... the messages were vile... very sexual. Also mention of him wishing he was still with her and how he screwed up by leaving her. Found out they had dated in 2010 for a few weeks. Anyway, so it all went to shit. We fought like mad, me and her and me and him. I could have wrung his neck. My friends all told me to get over it as it happened 2 years ago. Other friends told me to leave him. So now, fast forward 3 weeks. She went into my work acting crazy now work isn't giving me any hours because the cops had to be called on her. She has admitted she's a homewrecker and thinks it's hilarious how I never knew about it all and says my husband is a piece of shit and I must have a "wide set vagina" and all she was doing was trying to "make him feel good". From what I know nothing was ever physical it was all Snapchat and fb messages. Doesn't make it feel any better. I just discovered I'm 5 weeks pregnant. I'm keeping the baby. We went to marriage counselling and he broke down going on about his shitty childhood but I felt like he was making excuses for his crap behaviour. I am mad as hell at them both. She is making my life a misery but it's his fault this has happened! I don't trust him. I do love him. I do want to leave but I don't. He's trying but it all feels different now. I've got too much on my plate right now to make major decisions. I feel so lost. I don't even know what I'm asking for but can any one provide some support, comfort, advice? I don't really have anyone I can talk to.