Question

So, my fiancee and I have been trying for a baby. We're getting married next month but wanted to start sooner since he is leaving two weeks after the wedding for basic training. We had sex the couple days I was ovulating, its been three weeks, I don't get my period for a couple days but I was wondering if it is too soon for symptoms. I'm just having such bad cramps and I'm so fatigued I could barely keep my eyes open this morning and I had slept so well all night long.