I agree that you should speak with your doctor and counsellor -- you can express your concerns about going up to 100mg to your doctor and why he/she has recommended it for you...I also take Zoloft and started off at 50mg, then to 100mg, 150mg and now am on 200 mg a day for about 4 months now...it was my psychiatrist who recommended it to me...
I hope this helps and hang in there!
B