7w2d US & measuring behind :(

Sophie
Several years ago, I had a blighted ovum and a miscarriage around 16 weeks with my daughter's dad (we are not together anymore). I had to get two D&C's (I ended up passing the baby about a week after the first D&C). About a year after that, my husband and I wanted to try for a baby. We tried for over 2 1/2 years to conceive. I had to undergo two surgeries to remove scar tissue from my uterus from the D&C's I had. It only took me two cycles after the second survey to conceive. 
At first I was thrilled and announced the pregnancy about 5 days after I had found out. I was worried that I might miscarry again but stayed positive and hopeful. I had my first scan at 5w1d. Everything measured and looked good. You could see the yolk sac which meant I didn't have a blighted ovum. I was told to come back in a week to see the heartbeat. The next scan is what I was most nervous about. I needed to see the heartbeat for reassurance. I went in the following week for my 6w1d scan. No heartbeat. There was growth since the last scan though and the rest of the pregnancy looked good. I went back in a week later to check the heartbeat. This time there was finally a heartbeat. Unfortunately, the heartbeat was slower than it should have been. It was about 70-80 bpm. The baby and sac are also measuring behind about a week. My doctor doesn't seem concerned yet since there's a heartbeat and growth since last time. He also said the dating could be off by a week. I have to go back in another week to check the baby again. 
I'm trying to stay positive and hopeful. Sometimes it's hard. I'm definitely not feeling the excitement that I felt with my first pregnancy. I'm too scared to get excited. I hope that when I go in for my scan next week, the baby will be fine!
Any and all prayers are welcome!🙏🏼💗