I'm not sure that 30 to 100 strands is a lot as in normal/average hair loss. It may be a lot for you but you may just notice it more at those times. I suppose some meds could cause hair loss. I've noticed an ebb and wane in hair loss but I couldn't say what the cause was in either case. This may be interesting to you: How Hair Grows, Thinning Hair, Hair Loss Types and Causes