I got a love note, wat do i do?

it was like one of those hallmark ones, "p.s. i love you" and i got it in my locker, i think i kno who sent it, but he's going out, he's sweet 2 me tho, saying stuff like "u have beautiful brown eyes" and doing stuff like he is in front of me in line and kinda nudges my leg with his foot and he's like "oh my bad" so how do i act towards him? like i kno or not? nicer or the same? it might not be him, but the guy who likes me was absent that day, so i kno it wasnt him, because i didnt get the note till 3rd period, and the guy who i THINK gave me the note has 2nd period in my homeroom... and he treats me the best (he's the sweetest 2 me) but he's going out with another girl...