I have been working through the Art of Problem Solving Volume 1. I was a competent, though by no means excellent, maths student 20 years ago. AOPS was exactly the refresher needed to find those neurons again. Everything came back. However, had I jumped right into Trigonometry, I too would have been feeling like part of my mind was erased.

The math will come back, but you need to sit down and give yourself a structured program and, most importantly, time to actually do some exercises.