please help!

alright ladies i need your help asap. my boyfriend & i have been dating for 1 month but have been good friends for over a year, this past month i’ve pretty much been staying with him about every night. we’ve been spending so much time together that we’ve been arguing like crazy over stupid stuff. the thing is that i see girls names pop up on his phone and i’ve asked him and he says that they are friends from high school and stuff but that i have nothing to worry about. the thing is he’s been on his phone way more in the past week or so and our sex is way down. we used to have sex about everyday or twice a day and now we have sex about maybe 1 every 4 days if that. This morning i asked what is wrong and he keeps saying he doesn’t know but that maybe we should spend a couple days apart which we already discussed is causing our problems. What do you think? has anyone else gone through this? help please 😭😭😭