Negative blood test but pregnant?

Can anyone share their experience with this? Or know someone who has had this happen?

I’d be about 8/9 weeks. I have all the symptoms. My breasts and nipples are the worst. My nausea is on and off and I smell everything so strongly. I’m also cramping. I’ve been pregnant before and this is exactly how I felt with my other pregnancies.

This is not wishful thinking because we’re not trying to get pregnant. We’re in the process of kinship to adopt our daughter who is 9 months and my twins are 11 months SOO with that said I’m not in denial about not being pregnant. 😂

I got an ultrasound a couple weeks ago and they found a 4mm mass in my uterus. Since my blood test was negative they’re saying not pregnant. Great! So why do I feel pregnant?