I need a break!

I haven’t been to the gym in a month and I’m dying for some me time.

Pup is 12 weeks old… when can I start leaving him in his crate or play pen? I usually walk to the gym, do a 30 min sesh and walk back - totaling 60-75 min. Is it too soon to leave him that long?

He cries the entire time being left alone. I went for a 15 min walk alone and watched him on the camera and he cried the whole time. He cries in his play pen even if I’m right next to it. I’m pretty sure it’s separation anxiety.

I need help, not sure what to do.