How soon to take a pregnancy test!!???

Cassie • Mom of 5
Hi!
​I was wondering how soon can I take a pregnancy test? I am on day 18 of my cycle. I would normally wait until af is late but my husband leaves this Friday (May 16) to go work for the summer half way across the country. Since I won't be able to go with him I was wondering if I could take a test before he leaves!!?? Would that be to soon??
​Thanks :)