Why does he always ask me that???

my boyfriend doesnt trust me anymore. he thinks im cheating.. and i've read a couple of answers on other users and it means he's cheating. but could it be tru. he keeps asking me that. and he keeps asking if if i really want to be with him and if i'm sure about it. he also lives and 1 hour 30 mins away frum me. i dont get to c him much. :( and ppl say im dum cuz he could b cheating. but he's always txting me and calling me 24/7. but now he keeps getting txt messages and fone calls cuz i can hear tha beeps when we talk on the fone. he says its his mom, or his cuzin or his best friend. this used to never happen and now its happening all the time... HELP PLEASE. tell me wut u honestly think...