am I over reacting

I am pregnant with my husband and I's 3rd child and he has been staying up late playing video games and I took his phone from our son this morning and saw that he's been texting a female that he played games with and they have been sending selfies to each other and sexual memes and he told her he liked her tattoo in her chest!!! Now idk if it's just my hormones or something but that really pisses me off like I don't talk to other guys unless they are his froends to and even that is a hello how are you and then that's it. So what do y'all think?  I was so upset that I deleted and. Locked her number on his phone and deleted the messages they sent but it still shows up on his messenger. I almost texted her myself and was gonna tell her that if she feels like she needs the D then she needs to get with her husband and to leave mine alone but I didn't. And now he knows cause I just asked him about it and he said it's no big deal and dosnt even care Uptade*** he just told me that if I'm going to be that untrusting then I need to leave