Anxiety about sleeping next to another person

I have a recurring issue that I've struggled to find a google answer for and neglected to bring up during prior therapy sessions for anxiety.

I just started a new relationship after a couple years of being single. Last night we shared a bed and I wasn't able to sleep the entire night. I had this steady, mounting panic attack made up of racing thoughts (nothing negative, but fast and constant), stomach cramping, nausea, and eventually diarrhea the next morning. The nausea persists for at least a full day. I've had this at the begging of every new relationship, as well as just sharing a room with someone, in general; so, I don't think it is sexual intimacy related. My first incidence was at an elementary school sleepover and it has persisted into my adulthood (happens when rooming with friends or work colleagues when sharing hotel rooms for road-trips and conferences).

I've been diagnosed and feel like I've overcome Social and Relationship anxiety, and I work to avoid situations that trigger my claustrophobia. Acute panic attacks for my claustrophobia were treated in the past with lorazepam and I'm tapering off sertraline, which I'd been taking for 7 years.

Any ideas on what the issue/trigger is? Are there any ways to prevent this from happening without medication?

could it be something to do with worrying is that person is okay?. if you fall asleep, will your partner be okay?

I don't know how much help this will be, but I have a fear of people collapsing or not responding at any moment, and I know if I was put in that situation I'd be shaking the person (litirally shaking them) to make sure they are okay, awake, responsive, all that

so could it be down to that?. about you don't know what will happen to them if you sleep?

Hello and welcome to PC!

Maybe it’s just new and different from your routine. Do you eventually get comfortable sleeping with the new person? It’s very intimate to feel so trusting to be vulnerable and fall asleep with another person in the room.