Being on SSRI, I experience somewhat the same problem: even with high dosis (50 to 70 mg), I only get like 30 seconds of visual overlay, and thats it. I will be getting of the SSRI in march if all goes well, and I plan to wait 6 weeks after that to try dmt again, the reason being that I want my receptors clean, and a few days just is not going to cut it in my experience: I tried like two days of SSRI, then taking oral dmt+maoi ('godlike' dosis), but all I did was purge. Not even visuals. So...
I also am worried about stopping medication. I told my shrink I wanted to do dmt, and he was worried about that, then advised the two days break in ssri (to avoid seratonin overdose). He also told me that I should keep taking the ssri for a full year after my last depression, or it would risk coming back, in which case I would have to take it for like 2 years. Something about rewiring the neural pathways in the brain.
So 'just' stopping medication seems pretty risky. Perhaps you should consult your shrink about it, and get off the medication in a safe manner, then wait another 6 weeks to clean your receptors, and then try dmt. It’s a pain to have to wait, but you cant take risks with your brain. I know a few people that cut their ssri/antipsychotics who then plunged into the deep end so hard. Just my two cents. Wish you all the best.