I F16 and my Bf M15 have been doing LDR but he seems so distant 😖

So we starred dating the beginning of the school year he’s a freshman and in a sophomore I was dating this junior let’s call him L so me and L met on insta I followed him cause I thought he was cute then I met my bf we’ll call him H so me and H got close but I was still with L, so idk how it happened but I started dating H while I was dating L (which I feel bad about) I broke up with L and he made a joke saying “you should get with H you guys look good together” so I did well to his knowledge I did, so Me and H have been dating for 9 months now and once school ended I went on vacation and since that it’s been really dry and weird, my bf H said that we should have distance cause his BPD isn’t as bad when he’s just with his friends and that lwk hurt but I didn’t say anything I just started looking into things deeper like his note the song was saying how like this guy has a girl on the side and a gf and how he wants to do the things he does with his gf with the girl on the side and I just don’t know what to do PLEASE HELP🙏 or give advice anything is appreciated 😖 (idk if this matters but we argue a lot sometimes like once or twice a week my mom and sister in law don’t like him but I just don’t know if im ignoring red flags or if it’s a “I can fix him”
Thing or what🫩)