Husband chatting with female friends on the internet

My husband of 3 years hides his internet social life and whenver I have looked in his phone, i have almost always found random girls whom he has private conversations with- while Im sleeping. He says he is entitled to his privacy and has friends who he talks to and it is none of my business. Obviously as his wife, it is upsetting for me that my husband hides his female friends who he has met online. I have always told him, i dont mind if he has female friends- just dont hide it from me!! Nothing has changed in all these years. Im not sure why my husband has this online addiction- we have no kids- i am not sure why I should tolerate this? He does not care about my feelings and does not plan to change this habit. He also never apologizes, he always covers up by saying, “the conversations are meaningless” He also goes on to blame me by stating that I am “insecure” and I am the one who has issues while what he does is completely OK.

Anyone experience anything like this? What should i do?

He says- “I can talk to anyone in front of ur back or behind- I’m an adult- u don’t need to be so insecure about it”