Are you throwing single, powerful techniques, or multiple, faster ones? Combinations are key. Find a few and practice them until they are automatic responses. Never throw a single technique. Never throw a single kick. Always combinations. Backfist, reverse punch, ridgehand. Front kick, round kick, hook kick side kick. Front kick, land with backfist then reverse punch. Go-go-go; don't stop.
Practice backfist. Lots of opponents don't train to defend against them.
For practice, when you are sparring in the dojang, NEVER put your foot down. Spar with your leg framed for a roundhouse. Kick from a chambered position. From that position you can throw round, side, hook, even front kicks. It will build your speed and stamina.
Point sparring is NOT self-defense. You have to fight and train differently for point sparring. Most, if not all your techniques (except reverse punch), should be from your lead leg or lead hand. No kicks from the rear leg except spinning kicks.
As someone has already mentioned, learn to spar from an "open stance". That takes the round kick away from your opponent, which is the primary point-scoring kick.
Learn spin defenses. You said you like spin back kick. Also do spin backfist and spin hook and even spin round. (The spin round kick is weak, but deceiving and scores well in point sparring.) The "point" advantage to spin defenses is that your opponent will often hit you in the back (not your fault) and they cannot score that way.
If you want to learn how to defeat kicks with hands, go to a Kenpo or open tournament and watch the Kenpo guys. They are great with their hands.
Point sparring is not fighting. It is a game of tag. Your techniques do not need power or penetration; they need speed and light touch. Train for that and you will find yourself winning matches.
RELAX. Have fun. Tense muscles can be powerful but they are SLOW. Relaxed muscles are fast.
Good luck!