How soon should you meet your SO's friends when dating?

Curious how soon you met your SO's friends. I'm in a situation where he has a group of guy friends and a separate group of female friends that he goes out partying with, and he never introduced me to either. We dated for seven months and going on the second month of being in a official relationship. I do feel uneasy that I haven't met his friends. I did bring up casually that it would be fun to go ice-skating with friends together, and he was excited about the idea and said he would bring his female friend group along so I can meet them. But I just found out that he's hanging out with his friends after work at night, but he didn't invite me to meet them. Not that he has to tomorrow, but it's just that it made me feel uneasy knowing that it could be with his female friends, and told me that he will be "lacking of replying" to my messages. He's never told me that before