I always feel left out with my friends, how do i stop feeling so left out?

okay, so i have 2 friends, and (i know this will sound stupid, but it hurts cuz im so sensitive) they always do stuff like, 1 time we were thinkin of nick names for eachother, they decided i was gupy(like the fish) at first i liked it, then they decided they were both cats, so they were cats n i was a fish ohmygosh i wanted to cry, and another time, they both got Dr, pepper, n i got a coke, idk y but i just get so upset about this stuff, they do stuff like that all the time, they'll be walkin side by side, n ill be walkin begind them,idk wat to do to not feel so left out, theyre the most best friends ive ever had ever (btw im 13) we have so much fun together but................... i always end up wantin to cry cuz i feel left out, any1 got some advice for me, i really need it, ive been depressed lately.... :((((