New relationship - Is it okay for him to still be friends with his FWB?

Hey everyone, I'm newly out and have entered my first relationship with a guy. I wouldn't mind some advice as I'm new to relationships in general as I didn't date while in university. It's been a month and both of us have only been out for under 6 months. We became close and were more of friends with benefits about 4 months ago as he said he didn't want anything exclusive and wasn't ready for a relationship. Eventually I developed stronger feelings for him and broke things off as he had at least one other "hang out bud" and he seemed confused. We had a good talk and he kind of hinted that he was confused and not ready and thought maybe he would become more serious with his other FWB. I was really hurt, but we remained friends and organically started hanging out almost every day and things started up again a couple months ago until he asked me to be official / boyfriends as he was ready and said he realized how strong his feelings were for me. Things have been going great and we discussed that we are exclusive. I was mature and polite and let anyone I had been casually dating know that we couldn't hang out anymore, and I kind of assumed he did the same thing, so I haven't specifically asked him whom he talks to etc as I do trust him. This weekend I noticed that he's started liking his ex-FWBs social media posts after not liking anything since we started being exclusive. I don't think that they are seeing each other in person at all as we are nearly inseparable, and I have no idea if they still talk over text etc. The relationship seems very warm and he has been very open about how much he likes me and Im super happy with how things are going. I care the world about him. I haven't noticed any of the negative relationship red flags of him pulling back etc, and I feel like I"m probably being a bit unreasonable by allowing this to bother me - But given the situation and how much I was hurt by it previously, Im having trouble figuring out how I should handle things. Im typically not a jealous person at all, and I know I should not put much weight on social media likes etc, but it makes me uncomfortable that he is still in contact with a FWB that he was sleeping with a few weeks before we started dating. Should I bring this up with him, or is it really none of my business as they only were light friends whom occasionally hooked up? I feel like its not fair for me to ask them not to talk at all, but I find myself feeling insecure and seeing the likes brings back a lot of hurt and bad memories, especially when he stated that they might become more serious when I broke off the FWB things initially. Am I over reacting? How should I approach this?