What to do about a bf that constantly likes to call u a lier...im soo sick of it PLZ any advice?

how do i handle my bf.. he keeps treating me and accusing me of cheating on him and liking someone else . all becuz my little cousin is texting me i no for him it is out of the blue but there is a reason why is has been blowing up my phone and i don't think as an independent woman that i am supposed to bow down to him and give him my phone so that he can go through it and continue to call me a liar. i have never cheated or done anything like that... so i don't no how to handle this i on my own pay for this phone.. he has no need to go through my things yet he still continues to call me alier.. he always wants Control over everything of mine and i love him but he is just getting to the point of me walking out i cant take this anymore... how should i handle this... i dnt want to give into him and let him just have my phone.. its none if his Business if i don't want him to know i mean even tho we have been together for years i mean he should still respect my need for privacy i should still have my own need for it shouldn i ...i just don't no what to do about this anymore