implantation cramps or miscarriage??!

Hi ladies. I'm currently 5w1day after my first round of <a href="https://glowing.com/glow-fertility-program">IVF</a>. I was so excited and shocked when we got our positive beta. I had my second beta a week after my first and it was not as high as it should have been.

first beta 9dp5dt:141

second beta 15dp5dt: 819

needless to say, I'm freaking out. the nurse told me to remain "cautiously optimistic" but I'm just terrified that I'm going to miscarry. I have been having pretty consistent cramps over the past week or so. they're not unbearable, but they're definitely freaking me out. I don't know if it's just from implantation, or if it's the beginning of a miscarriage. I haven't had any bleeding or spotting at all. I have another blood test and ultrasound in a couple of days but the wait is killing me and I'm reading into every single symptom. any and all words of encouragement are welcome... especially if what I'm going through resonates with you at all.