Low HCG and no gestational sac at 5 weeks on transvaginal ultra sound

Tracey
Yesterday while out with my husband I felt like I had passed something. When I got home I noticed a lot of brown mucous and contacted the early pregnancy unit. Today I had a transvaginal scan and there was no visible signs of pregnancy. I also had blood drawn and my HCG is at 340 and progesterone is 60 o am worried sick as we had a missed miscarriage in February at 8 weeks. Any opinions?