In total I've probably done acid about 10 times, and mushrooms about 10 times, over the course of two years. I've also done mdma about 6 times over that time as well. The last time I did it, about two months ago, I mixed LSD with MDMA and tripped hard. The following day I got out of bed (from not sleeping all night), and stood up to realize I had the following symptoms; cold and clammy feet, severe exhaustion (barely able to stand), slight visual disturbances, slight derealization, and a bit of misperception (the same kind of perceptual flip-flopping that one feels while one the drug, similar to the effects of alcohol). These symptoms lasted for about 4 days. The other symptoms faded as the exhaustion did. I know that this seems relatively normal, most people end up feeling pretty terrible for the days following a trip, but it wasn't normal for me. Usually, even after the most extreme trips, I could wake up and go to work, getting by feeling as though I was just hungover.
I may have been experiencing an extreme come-down effect from the mdma, which I hadn't touched for about 6 months prior to the date. I was already low on sleep, and didn't sleep at all the night following the trip (which was an overnight trip (which consisted of a large and exhausting hike) anyway). The symptoms seemed to match up perfectly with the descriptions posted on HPPD forums though, and I'd never experienced a come down of any sort from MDMA, other than an apathetic feeling of indifference for a couple days.
So here's my question, would it be safe to do either LSD, MDMA or mushrooms again? It seems like most of the severe HPPD cases last at least a month, mine lasted 4 days before I was 100% back to normal. Am I just being overcautious? I know I didn't have a severe case by any means, but if I repeated my use of any hallucinogens, could I possibly end up with a severe case?