Maybe Baby?

Went in this past Monday for our first ultrasound at 8w2d. Baby only measured at 6w1d and the fhr was only 91bpm. (which btw myself, hubby, my daughter, and both grandmas were there to see) There is no way I ovulated later because we were on fertility drugs to induce ovulation to begin with and I got my first positive pretty early around Dec 7th. Doc says there's a 60% chance it will catch up on growth and 40% chance I'll miscarry. (I honestly think he was just being nice). We had been trying for almost 2 years to get pregnant and if my sweet little bean doesn't make it idk what I'm going to do. I'm having the worst anxiety which I'm sure isn't helping the situation but I can't control it. I go back on the 22nd to see if there's been any progress but it just feels so far away given the situation. Every little gas bubble, every single cramp, every time I need to use the restroom.. it's killing me. I feel so incredibly helpless and lost right now. Does anyone have any advice on how to stay calm until I go back? or has anyone had the same situation with a positive outcome? please give me some hope yall.