I can't seem to dissociate on dxm

I'm 170 pounds and tried to trip on dxm many times, and never get a dissociative trip. When I took 300mg, the best it felt was like a combo of an alcohol buzz and low dose spravato/ketamine. On 600mg, it felt like I was going to die, followed by puking 3 times, then felt like 300mg again. Yesterday I tried 960mg, and it felt the same, except I had a very bad headache, so I couldn't enjoy the high.