How to have the confidence to ask him if he likes me?

this guy has been confusing me soo much, and he gives me mixed signals. he talks to me 24/7 constantly one day, flirt and everything. the next day, he won't and its just like a huge cycle. I like him a lot, it seems like he likes me too? but im not sure if hes just messing around or just flirting with me? but i like NEED to tell him because im going insane, and its taking over my life. Idk how to tell him that I like him, and that i wondewr if he likes me too and all thiss stuff. i barely see him .. so yea, I was gonna do it over the phone.. but im scared.