Unfortunately there isn't much you can do being on the male end of this relationship if she doesn't want to take a pregnancy test.
Ask her if she has had any pregnancy
, such as sore nipples, mood swings, or
here's a good one, ask her if she'll take her temperature first thing when she wakes up in the morning. Typically, if she's not preg, she should have a temp around 97-97.9. Women who are pregnancy tend to run a higher temperature, such as 98.6 and higher.