I am the complete opposite... I love rollercoasters. I actually travel all over for them and has been a big hobby of mine since I was little.
I currently have been on nearly 250 different rollercoasters... Which include the tallest/fastest ones in the country. I was just in Charlotte for the opening of Fury 325 which is the tallest chain-lift coaster on the planet. 325ft, 95mph... smooth as butter, amazing ride!
To be honest, there is nothing to fear about them. Extremely safe, most modern ones are very smooth and far less intense than rides built 20 years ago. In fact, at my home park Cedar Point here in Ohio (has the 2nd most coasters of any park in the US), their 50ft wild-mouse coaster had more G's than their 310ft coaster, rated one of the best in the world.
Size means very little with rides and intensity. Some of the largest rides are the "weakest" while smaller rides can have a much bigger punch, intensity wise.
What park you going to? I can help guide you on which rides will be best to ease in with, or which ones to avoid. It is easy to know just based on the manufacturer and style of the ride.