CD 41 I'm 13 days late

So I have no symptoms of being pregnant ( only mild cramps here & there) & I took a cheapie on Friday & it came back negative. I had a doctors appointment today but they had to reschedule it for tomorrow. Do you guys think I could be pregnant? LMP Sept 10-13 the whole month of September I've only did the do 1 time that was on the 7th. I'm an Army wife so my hubby was away for training & when he got back we did the due but still no sign of AF :(