If you are taking 500mg in one session you either have a monstrous tolerance (which I doubt since you say you are new to MDMA) or your product is cut to shit or something other than MDMA entirely. Get a testkit. I do not believe you are ingesting pure MDMA. I can tell you that if I did 500mg of pure MDMA for my first few times I would have ended up calling an ambulance on myself without a doubt. Or probably my mates calling one, as I would not be able to even hold a cellphone anymore, let alone call someone
Even after years of rolling and with a high tolerance the one time I took 500mg it was too much (let me mention I took 500mg by accident, not intentional). I was rolling way way too hard and was near a collapse. Blacking out, dreaming while awake, hallucinating like crazy, loss of muscular control, balance problems, very irregular heartbeat, drenched in sweat and with an eerily white skin color. The only thing that stopped me from getting myself to a medic was that I was too wasted to realize I had gone over the edge and I had lost my mates in my stupor. I was actually enjoying myself because I barely knew what was going on. At one point a team of medics that roams the crowd saw me, looked at me like they had seen an alien and wanted haul me off in a hurry to an ambulance. I remember running away from them thinking "you'll never catch me, you kill-joys!". Damn that was stupid, I'm still mad at myself for that night after years have passed. And as I said this was after years of rolling and with a very high tolerance
Buy a testkit and test everything before you ingest it. Find another dealer as your current one is ripping you off with fake or very bad product