Alternate to shaving?

So I've been shaving my underarms for the past year or so. I'm 13. I just use a disposable razor and shaving cream you know, but I can never get all of it! It is so freakin annoying! So I can't ever really wear tank tops, and if I do I don't lift my arms all the way. I know it sounds gross, but I get almost all of it...I just can never seem to do it perfect. Sooo is there some more guaranteed alternate to shaving my underarms that will get all of the hair?? Please help me it's really annoying. Don't laugh at me :( No matter how many times I go over it with my razor I can't get it right.