Should I be worried??

So on 1/15 I took a pregnancy test and it came back positive. It was a very faint line but positive. I went to an urgent care because I started to get pelvic pain. They did. Pregnancy test, blood work and an ultrasound. The test came back positive, my hcg levels was 81 and they didn’t find anything on the ultrasound. According to my LMP I’m 4wks4 days as of today. My doctor recommended me see a doctor the very next day to get another blood test. So on 1/16 I did another blood work and ultrasound. My levels were 134. Ive heard that the numbers are supposed to double and so I’m a little worried. This is my first time being pregnant and I just have so many questions.