Is he cheating on me?

so we been going out for two months after the first month he got my name tattooed on his chest. but before we went out i met him at my aunts bar and he would always sit wit a girl that drinks and dances for money and is capable of anything for money she cares less in who he is with as long as she gets money but he told me he didnt want nothing to do with her and never did anything with her but recently he has been acting strange and asked me a question out the blue "what would you do if i cheated on you" and i said id leave and he repeated the question but he said if he was drunk and cheated and i repeated my answer well after that i asked my ex about it wich is a very good close friend and he told me that the girl i think he's cheeting on me with has told him that she has been sleeping with my boyfriend, i dont deny the fact that he maybe has because before my ex told me that the day before he got a call and said "ill call you right back yea" and thats usually what he tells me when he sweet talks to me and he didnt want me to chek his phone so when he got out to get gas i snatched the phone up and it was under code 1 and my dads number is under code7 like he has nickname for everyone in his phone but that just seemed awkward so i kept the number and after my ex told me i asked what was her number and that was her number under code one so i sent him a message and told him it was done because before this he had a issue with drugs and i told him if he didnt stop i would leave and he has done it twice since he promised so i went home and confronted him and told him i knew everything and he went balistic broke his phone his 700 dollar rosary and was hitting himself after that i asked what was that number doing there under that name and why did he delete it that same day and he tried to deny it was her so i called her and she answered.also he supposedly left his car keys with his friend two hours from where we live and he has supposedly been borrowing a car and papers were all over the car with her name ='(..what do you think