Amy, there's nothing wrong with being paranoid. Much of self-defense or personal security centres around mindset - you're working toward the flipside of "Look like food, and you will be eaten."
OC spray (pepper spray) tends to be of limited utility - there are people like me who could probably get more use out of the stuff spraying it on a burrito for lunch than if you were spray it in my face. Just the way things work - I happen to like very spicy food (my grandfather spend the best part of 30 years trying to find something "too hot" for me to eat. Found a few things too hot for him to eat, but nothing I didn't enjoy...)
As far as self-defense techniques, the simple things work best. I've been teaching my wife (5'2", bad knees) a mix of judo, aikido, and dragon style kung fu, with some Armed Forces combatives thrown in - but the best moves I've shown her are the ones that are borne of pure reflex. How good is she? I'm 6'3", 265#, and she can toss me around the yard during a practise session (and I don't let her - she just does. She's learned well...)
In a physical altercation, you do have a certain advantage being female. I could break a man's knee, and I'd get sent up for Assault with Intent and Malicious Wounding - you'd get self-defense. So:
Knee to the groin
Knee to the meat of the thigh (both of these should be delivered sharply. Both are effective.)
Snap-kick to the knee. If from behind, it will force it to bend. If delivered to the side, the knee may hinge in a new direction (and it will hurt all to be-damned.) If from the front, it may make the knee hinge backwards.
Shin scrape/foot stomp. Most effective if you are grabbed from behind - forcibly drag the side of your foot down the front of your attacker's shin, and drive it smartly into the top of the foot. The shin scrape will cause a great deal of pain, and the stomp will likely fracture metatarsals and make it difficult to stand.
He won't take his hands off of you? Don't try to remove the hand - just grab the last two fingers and try to make the fingernails touch the back of the hand/wrist. If he doesn't let go, you'll end up breaking the fingers - which will make 97/100 people let go (most people don't have that sort of discipline - those that do, aren't likely to be pulling street grabs just for fun.)
Once upon a time, I "ran deposits" for a family store. In a college town. Next to a bar. My favourite at the time looked like a leather sock - it was a double-stitched long bag with thirty dollars' worth of loose quarters in it. It was a "legal sap" - quarters can be explained away as laundry change, automat change, ... Had to use it once - the effect was most gratifying, and I understand the guy woke up in Holding two hours later with a very bad headache.
Do Not Panic - there should always be a part of your brain "wargaming" - if this, then that. I know a part of mine always is - and it's saved me on occasion. It seems difficult at first, but once you get used to it, it will be automatic. Having a plan - even a half-formed one - when the flag goes up will put you ahead of the game.
And, don't be afraid to be paranoid (doesn't that sound odd?) Some part of you should always be worried in this day and age, and it's good to expect an attack. It's when the paranoia takes over your life that you are having trouble, but even paranoids have enemies.
"Paranoia - the unreasoned feeling that people are out to get you.
"Depression - finding out that you're right."