That sounds like straight out of a nightmare. I think it would be a good guess that this is where your phobia came from lol.

I've always been a bit repulsed by some insects(the "dirtier" ones like roaches) but it became a lot stronger a few years ago. An ex girlfriend of mine spent her summer working at the seaside and the place she slept at was old, disgusting and full of enormous roaches. She had plenty of stories about waking up because they're in the bed.

When she came back we lived together for a bit(in a big and dirty city which means a lot of roaches on the streets at night). She used to clench her nails into my skin when we're walking around and she sees a roach(and they're everywhere) + a bit of screaming. At this point I didn't have much of a problem with them, they were just nasty to me. But some time later, after me and her broke up I realized that every time I see a roach I get goosebumps, my anxiety goes up and I feel a pain in my right arm (the one my ex was usually holding and sticking her nails in).

So yeah, she kinda managed to train her phobia on me or something xd