Am I a terrible person?

So, I’ve been pondering this lately along with talking about this with my therapist…but I just need to know if someone has ever felt this way. 

I’ve been with my s/o for about two years now and don’t get me wrong, I LOVE and adore them. I’d do anything for them and they truly are my other half. 

My mind although…I feel incredibly guilty because of the way my mind functions. I become incredibly attached and start imagining myself doing *things* with people I barely know. Again, I would never cheat on my s/o and I feel incredibly guilty for even thinking of these things but why? 

This has happened continuously with every person I’ve ever met and I know I sound like a shitty person but it’s not me. I’m not even sure what it is anymore. 

I just wanted to see if anyone here relates and can give some insight. Anything would help. 

To maybe further context, I was initially diagnosed with bipolar 1 but my new psychiatrist believes I have bipolar or bpd or a combo wumbo of both since they are similar. 

Thanks y’all :(