Are you breastfeading, because sometimes that can mess with your cycles. Also it does take a while for your cycles to get back on track...so Ive heard...
If you are still unsure about it, ask for a blood test.
And I agree with Becky, I would not want my husband to be away while I was pregnant. You need someone there to comfort you and just be there for you if you need him. Its not that far off.