About once every 5 days to a few weeks a depression from hell hits like a tsunami. What could cause that? It gets so bad that I move like a snail like a person does when they have a really bad flu or like I'm 100 years old. I feel an ache in my soul that's indescribable.

All I know is that I can't do this much longer. It's getting worse. I have no idea what's causing it. When the depressive part of the cycle ends I get hope and somehow convince myself I won't let myself get depressed and suicidal but sure enough I change into a completely different person and get extremely depressed and start doing suicidal planning. It's just horrible. It has a terrible effect on my body, which aches for days after it ends. The only good part is that I sleep like a rock for a long time while my body heals.

None of my psychologist ever told me what's causing it. She had me do a cat scan which didn't show anything so it must be psychological. I was diagnosed with a lot of disorders but the only one that has cycles seems to be BPD, but I don't know if BPD is known to cause such endless horrible cycles. I was also diagnosed with DID by another psychologist but I don't know if that could cause this.

I took DBT and EMDR but it didn't seem to help me.

Any ideas?