Between Sizes?

Danielle • Mommy to a precious little boy born 12/17/15 and full time working mom! I love my little family!
I feel like my son is between diaper sizes right now. He's 7lb 4oz and 22 inches long. He's 3 weeks old and has been in newborn since birth but lately has been having some blow outs/leaks.  I heard that means it's time to move up a size but size 1s are HUGE on him! He's a long and skinny boy. 
Is it better to keep small for another week or try to go ahead and move up to the huge 1s? Has anyone else had this problem?