Beta levels

my first beta was on April 21, it gave 9. my second beta was on May 8, it gave 537, the third was on May 11, it gave 626. on May 15 it was 1251. on May 17 it was 1477. even I do not know how many weeks I have my period was on April 29 and in the ultrasound that I did yesterday you can not see anything because it is very early. I was having bleeding and cramping on day 13 and 14 but now I have nothing what do you think?