Most Helpful Guy
not necessarily, a person wants to have time to themselves some times. If he continuously does this yes but once is not odd, especially since you've seen each other every weekend for almost a month.
Most Helpful Girl
Why is it a red flag? If you’ve seen each other every weekend for 4 weeks it’s not unreasonable to give one a miss and catch up on what he usually does on the weekends. If he stopped texting or declined seeing you a few times then absolutely - but it seems like a bit much to assume warning bells from him wanting to catch up with his mates