Boyfriend still has a childlike mindset

Me and my boyfriend been together since he was 15 & I was 16 .. we are now 20 & 21 and he still ask me stuff like “what if I cheated on you” would you still take me back type of questions . And it’s annoying . We had this convo already I told him no I wouldn’t take him back . But then I changed my answer and said idk . I’m not in that position right now so there’s no way of me knowing what imma do . I don’t think I’ll take you back but who knows . But months later (today) he asked me again “what if I cheated? What if you found out I got someone pregnant” then referred to someone we know who went through that . And I’m like if you have anything to tell me then say it . If not stop bringing this up it’s really childish, we aren’t 16 anymore .

Also he’s in jail right now and he usually have me 3 way his friend . I usually never listen to the phone call I just put the phone down and go do something . Well that’s what I did this one day out after a few minutes I picked the phone up to see if they was still otp and heard my bf say to his friend “you really got a baby on the way , that’s crazy” then his friend said “bro you got 2 kids and a maybe” and my bf was like chill stop playing .. but I never thought anything of it . I just thought it meant we might end up having another baby when he come home but now that he’s asking me this stuff I’m kind of skeptical 🥴 but there’s no way my boyfriend will tell me if he cheated on me . He already told me he wouldn’t because he doesn’t wanna lose me but now that I’m typing it I realized how much of a red flag it is . And I don’t wanna be with someone who wouldn’t man up and tell me the truth if asked .