Did you jump right from 50mg to 100mg, without trying 75mg for a while. The sudden increase could be the culprit.

But dude, please, whatever is causing the feeling, stay safe! If you want to talk, I'm here to listen. Try to contact your doctor as soon as possible, and try to avoid sharp increases or decreases.

Personally, I got headaches, jitteriness and cognitive symptoms at higher doses, but I never felt sucidial from the Zoloft. Your brain could very easily be different though.