Can't use tampons??

I'm a 13 year old girl and I'm a virgin and I need/want to use tampons because I play volleyball and I think they will just generally be more comfortable. Today I tried putting one in for probably the 6-7th time and even tried multiple angles & it still didn't work. In all the times I've tried the farthest I've gotten it in is maybe a little less than a centimeter.. is it possible that the opening is blocked or just not big enough?? I used a mirror and it looked tiny. Maybe the size of a grain of rice or two. I'm using light size plastic applicator tampons, but not a name brand. Help please. Many of my friends have gotten them in fairly easy on their first try, and I'm very frustrated.