I don't know your exact body anatomy, but if I had to bet $100 on whether it's your hand size or not, I would definitely say no. Just about everyone, even people with extremely small hands, can reach four frets in a row. Most people can even skip one or two. If you hold your hand out in front of you and spread your fingers out, they should be more than wide enough to cover four frets.

So I'm not even really sure how you could be having a problem with this. Make sure your thumb is behind the neck so your hand can come up from under the neck.