When Are HCG Test And Transvaginal Sonogram Needed To Be Tested Again?

Hi! I had PROTECTED sex with my husband on June 12 and June 15. On June 18, I went abroad to visit my parents and went to the doctor to ask about my spotting that I have from time to time between my periods (December 2015 and April 2016). My American doctor said that it might be an yeast infection, but if it was yeast infection I would feel some discomfort and discharge would be white, not brownish. The Russian doctor examined me. She said that I don t have any infections and told me that I have to draw my blood to check my hormones and then to do a trans-vaginal sonogram 7 days after my next period is over. She told me that at this moment I can check the level of my progesterone. I did this (on June 25th) and it turned out that the level was very low. Several days later around June 30th I started spotting again for no reason. My period did not come. My last period was on June 4th. I did several home pregnancy tests, including hCG test in the hospital. All of them were negative. On June 11th I did a trans-vaginal sonogram. The doctor said that I m not pregnant. She saw a yellow body. It means that I ovulated, but my period did not start because my endometrium is not thick enough (13 mm on the 37th day after my period was over). She prescribed duphaston and told me to take the pills twice a day 10 days in a row until my period starts. It s already July 17th and I m still not bleedng (my last period was on June 4). I do not drink or smoke, I use condoms when I have sex with my husband. I ve never had unprotected sex. I am HPV negative and don t have any SDTs. Everything is fine with my thyroid gland, including blood (I m not sure about my hormones though as I cannot check them. Still waiting for my period). My periods were always regular and painless. I did not have any stress last month. I ate well. But last month was too hot in California (around 120F every day) and I was flying to Moscow where temperatures were around 90F. Can I be pregnant? Should I take hCG test again and do a trans-vaginal sonogram again?