need to vent

So me and my husband got into it this morning bcs I saw him and his ex have been texting back and forth he has two kids with her 12&13 they were married & divorced in 2011 then me and him met & got married 2012 we have 3 little girls 4,3 and a 3 month old. Well my problem is his kids are old enough why does he need to talk to her for. This is the 3rd time I see they have messaged each other the last time this happend was like 6 months ago and he told her then and there for her not to be texting his phone if she needs anything let his parents know & they would let him know. But I have a suspicion they have been texting ever sinc. So I saw the messages last night and confronted him this morning. I said So now it's ok for you & your ex to be texting back and forth. And he said uh huh yeah to everything I had to say or ask. And was laghing about it. I asked him why does he feel he needs to talk to her when he knows I'm not ok with it. He said that's the kids mom and he can't help it basically saying if she texts him he'll text back. So my problem is he doesn't respect my feelings I don't see how before he would have no problem telling her to back off but now he defends her and says he can't help it. I know she still has feelings for him & im sure he knows that shes been single and one thing could easily lead to another. I don't understand why he would do this and go against what we had agreed on. He doesn't respect me I feel somewhat betrayed bcs for one he has no business talking to her specially when she's telling him she was sad and other crap. and two by the looks of it he deleted most of there conversation. If he didn't have anything to hide why delete anything. And the messages were from the day me and him got in an arrangement and he slept in the living room which is now a habit he has. everytime we argue he goes and sleeps elsewhere instead of talking things threw. And the day before his birthday they were texting too. He also has her number saved under his daughters name when she has her own number. He also got her an iPhone and she's only 12 so that's why in the message the mom is telling him the daughter wants her phone. I don't know if I'm overreacting but when I told him how would he like it If I would talk to my ex he said I don't have kids with him and to do whatever I want. So that's an excuse to talk to his ex. I'm just not ok with them talking period she doesn't know her place I know that she tries to be super nice and tries to make my husband feel sorry for her. That shouldn't be his problem anymore. I just don't know what to do I'm extremely upset this morning when I confronted him he has nothing to say he was in a hurry to get out of the house and dust try to tell me that it's not what I think or nothing he said I'm crazy and was laughing I think that's what's more upsetting he thinks it's all a joke and he can do as he pleases and I have to suck it up. Am I overreacting how would you guys handle the situation? And lately he's very distant and never wants to be intamate he works like crazy even weekends. I'm just super upset and feel betrayed by him I'm this close to texting her and telling her to back off but I don't want make my self look like a fool bcs he's the one allowing it. And now i really don't know what's going on is she's the reason he's been ascting so weird. I just wish he would put her in her place and respect me as his wife.