OPINIONS!!!

So I am worrying about being pregnant or not, I had AF on may 11-15 and later that month had intercourse next cycle was due June 6-10 I did get AF but before that cycle I had a faint positive so when I started I knew it was a false positive I took one on the last day of cycle came out positive still, took many more test and still positive so they have calculated me to be 5 weeks and 5days now but when in for a Ultrasound and they saw nothing but I believe I conceived late in the month of may is it possible I may be a week less and possible to get a period while pregnant?