I take MDMA fairly fequently
^ The brain zaps that Si Ingwe mentioned are very common in people who've abused MDMA/ecstasy and taken large amounts or take it too frequently. You should limit yourself to a very maximum of once a month, ideally every 2-4 months or less. Any more frequently than that is going to make things worse.
Also as Solipsis mentioned, HPPD is something that is present even when you've been completely sober for a long time. If you're still using psychedelics, smoking cannabis, and more importantly taking MDMA (where MDA, one of its main metabolites is a psychedelic in itself) - then you're not sober, and as such it makes sense that you're still experiencing residual effects.
Also, you said you noticed "little squiggles" - could these perhaps be floaters? Try seeing an opthalmologist. I started experiencing something like this shortly after a psychedelic trip and thought it was linked, I went to see my opthalmologist and they said it was an unrelated PVD or Posterior Vitreous Detachment, which caused a sudden massive onset of floaters filling my vision.
These floaters were ever persistent and I couldn't seem to concentrate on anything else in my vision because they were so prevalent, so I asked her what to do, and she said to simply try and ignore them and they'll go away - so I did, and now I can't even see them when I try. I can still see some floaters but not nearly as many as before and they don't intrude on my vision.
There's also visual static/visual snow, where your vision becomes grainy like static on a TV - this is common and many people have it, and it seems to be worsened by various substances, MDMA being one that's notorious for it - so if you're noticing this effect it could be linked to your MDMA use, and you might need to tone down the frequency and amounts. In my experience Cannabis can also make it worse so you might want to cut down if you're a regular smoker too. Phenethylamine psychedelics (like the 2C-X series, the NBOMes and the DOx series) all seem to make it worse too, though tryptamines (like aMT, DMT, Psilocin) have the opposite effect.
When I'm high on Cannabis or alcohol my visual snow and floaters are most visible so this could be what you're experiencing.